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- As discussed in the paper, the focal definition also imposes an assumption of perfect indivisibility, despite evidence to the contrary of cooperative ownership (Myers 1921) and custom work (Gilbert 1930). To ensure that the results are not sensitive to this assumption, in Table C.2 I re-estimate these regressions defining diffusion as the number of tractors per 100 acres of county farmland. The regressions for 1925-1930 are estimated on a sample excluding the Plains states (North and South Dakota, Kansas, and Nebraska), where farmland was expanding rapidly at the time. The results are qualitatively similar to those in the body of the paper.
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Basu, Susanto and David N. Weil, “Appropriate Technology and Growth,†The Quarterly Journal of Economics, 1998, 113 (4), 1025–1054.
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Caselli and Coleman, “The World Technology Frontier,†The Quarterly Journal of Economics, 2006, 96 (3), 499–522.
Clarke, Sally, “New Deal Regulation and the Revolution in American Farm Productivity: A Case Study of the Diffusion of the Tractor in the Corn Belt, 1920-1940,†The Journal of Economic History, 1991, 51 (1), 101–123.
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- Column (2) controls for pre-1925 trends in the stock of farm machinery as a fraction of land values, a proxy for mechanization; Column (3) adds controls for the intensity of other major Midwest crops (oats, barley, rye, hay); Column (4) adds further controls for the distribution of farms by size (i.e., fraction <20 acres, 20-49 acres, 50-99 acres, 100-259 acres, and >260 acres) and the log mean farm size; Column (5) adds controls for substitute inputs (horses per acre, mules per acre, labor expenditure per acre); Column (6) adds controls for financial variables (farm mortgage interest rates and debt ratios); Column (7) adds controls for geographic and climatological variables (centroid coordinates, distance from Detroit and Chicago, quadratics in county mean temperature and annual rainfall, and intra-county variation in elevation); Column (8) adds controls for local New Deal Relief (AAA spending and FCA lending per harvested acre).
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- Column (2) controls for pre-1925 trends in the stock of farm machinery as a fraction of land values, a proxy for mechanization; Column (3) adds controls for the intensity of other major Midwest crops (oats, barley, rye, hay); Column (4) adds further controls for the distribution of farms by size (i.e., fraction <20 acres, 20-49 acres, 50-99 acres, 100-259 acres, and >260 acres) and the log mean farm size; Column (5) adds controls for substitute inputs (horses per acre, mules per acre, labor expenditure per acre); Column (6) adds controls for financial variables (farm mortgage interest rates and debt ratios); Column (7) adds controls for geographic and climatological variables (centroid coordinates, distance from Detroit and Chicago, quadratics in county mean temperature and annual rainfall, and intra-county variation in elevation); Column (8) adds controls for local New Deal Relief (AAA spending and FCA lending per harvested acre).
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- Column (2) controls for pre-1925 trends in the stock of farm machinery as a fraction of land values, a proxy for mechanization; Column (3) adds controls for the intensity of other major Midwest crops (oats, barley, rye, hay); Column (4) adds further controls for the distribution of farms by size (i.e., fraction <20 acres, 20-49 acres, 50-99 acres, 100-259 acres, and >260 acres) and the log mean farm size; Column (5) adds controls for substitute inputs (horses per acre, mules per acre, labor expenditure per acre); Column (6) adds controls for geographic and climatological variables (centroid coordinates, distance from Detroit and Chicago, quadratics in county mean temperature and annual rainfall, and intra-county variation in elevation); Column (7) adds controls for local New Deal Relief (AAA spending and FCA lending per harvested acre).
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- Column (2) controls for pre-1925 trends in the stock of farm machinery as a fraction of land values, a proxy for mechanization; Column (3) adds controls for the intensity of other major Midwest crops (oats, barley, rye, hay); Column (4) adds further controls for the distribution of farms by size (i.e., fraction <20 acres, 20-49 acres, 50-99 acres, 100-259 acres, and >260 acres) and the log mean farm size; Column (5) adds controls for substitute inputs (horses per acre, mules per acre, labor expenditure per acre); Column (6) adds controls for financial variables (farm mortgage interest rates and debt ratios); Column (7) adds controls for geographic and climatological variables (centroid coordinates, distance from Detroit and Chicago, quadratics in county mean temperature and annual rainfall, and intra-county variation in elevation); Column (8) adds controls for local New Deal Relief (AAA spending and FCA lending per harvested acre).
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- Column (2) controls for pre-1925 trends in the stock of farm machinery as a fraction of land values, a proxy for mechanization; Column (3) adds controls for the intensity of other major Midwest crops (oats, barley, rye, hay); Column (4) adds further controls for the distribution of farms by size (i.e., fraction <20 acres, 20-49 acres, 50-99 acres, 100-259 acres, and >260 acres) and the log mean farm size; Column (5) adds controls for substitute inputs (horses per acre, mules per acre, labor expenditure per acre); Column (6) adds controls for financial variables (farm mortgage interest rates and debt ratios); Column (7) adds controls for geographic and climatological variables (centroid coordinates, distance from Detroit and Chicago, quadratics in county mean temperature and annual rainfall, and intra-county variation in elevation); Column (8) adds controls for local New Deal Relief (AAA spending and FCA lending per harvested acre).
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Comin, Diego and Bart Hobijn, “Cross-country technology adoption: making the theories face the facts,†Journal of Monetary Economics, 2004, 51 (1), 39–83.
Conley, Timothy G., “GMM Estimation with Cross-Sectional Dependence,†Journal of Econometrics, 1999, 92 (1), 1–45.
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Duflo, Esther, Michael Kremer, and Jonathan Robinson, “How High are Rates of Return to Fertilizer? Evidence from Field Experiments in Kenya,†American Economic Review: Papers & Proceedings, 2008, 98 (2), 482–488.
Dupas, Pascaline, “Short-Run Subsidies and Long-Run Adoption of New Health Products: Evidence From a Field Experiment,†Econometrica, 2014, 82 (1), 197–228.
- Empirical CDF 1935 1940 1945 1950 1955 1960 Year 50% diffusion Empirical CDF Fitted logistic Notes: Figure shows the distribution of U.S. states by the year at which they attain a given level of hybrid corn diffusion, measured as the percentage of corn acreage planted to hybrids. Data from USDA Agricultural Statistics.
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- F Details of Labor Savings Calculations Starting point: U.S. labor savings from tractorization in 1944 (1) 1,700 Labor savings from tractorization, 1944 (millions of hours) Cooper-Barton-Brodell (1947) Calculation: Subset of U.S. labor savings in 1944 from Midwest (2) 1,169,154 Farms in Midwest with tractors, 1945 U.S. Ag Census (1945) (3) 2,002,662 Farms in U.S. with tractors, 1945 U.S. Ag Census (1945) (4) 58.4% Midwest share of adopting farms, 1945 Calculated: (2)/(3) (5) 992.46 Midwest share of labor savings, 1944 (millions of hours) Calculated: (1)*(4) (Assumes labor savings constant across mechanized farms.
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- Figure 3: Tractor diffusion in Midwest states, 1920-1950 0.00 0.20 0.40 0.60 0.80 Tractor diffusion 1920 1930 1940 1950 ND/KS IA/IL MI/WI Notes: Figure shows the path of tractor diffusion from 1920 to 1950 in the states that form the core of the U.S. Corn Belt (IA/IL) and Wheat Belt (ND/KS), as well as in two states with low crop concentrations and little of either staple crop (MI/WI). Data from 1920 to 1950 Census of Agriculture.
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- Figure 4: Estimated cumulative change in tractor diffusion, 1925-1940, all-wheat vs. all-corn 0.00 0.15 0.30 0.45 0.60 Coefficient estimates 1925 1930 1935 1940 Wheat Corn Notes: Figure plots the point estimates from the 1925-1940 specification in Table 5, Column 3, showing the cumulative change in diffusion for a county with all farmland planted to wheat versus all farmland planted to corn. The dashed lines bound the 95% confidence interval for each estimate.
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- Figure 5: Est. differential increase in tractor diffusion in counterfactual, 1925-1940 0.00 0.05 0.10 0.15 0.20 0.25 0.30 Aggregate increase in diffusion 1925 1930 1935 1940 Equalized rates Estimated rates Observed rates Notes: Figure plots the aggregate difference in tractor diffusion implied by the estimates in Table 3, Column 3, had tractors diffused as rapidly in corn-growing regions as they did in wheat-growing regions. Calculated as described in text.
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- Figure E.1: Reproduction of Griliches (1957) Fig. 1: Percent of corn acreage planted to hybrids 0 20 40 60 80 100 Percent 1932 1936 1940 1944 1948 1952 1956 1960 Year IA WI KY TX AL Notes: Figure shows the characteristic S-shaped hybrid corn diffusion curve for each of Iowa, Wisconsin, Kentucky, Texas, and Alabama, reproducing Figure 1 of Griliches (1957). Data from USDA Agricultural Statistics. Figure E.2: Distribution of states, by year at which given level of hybric corn diffusion attained 0 .2 .4 .6 .8 1
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- Fishback, Price V., Shawn Kantor, and John Wallis, “Can the New Deal’s Three R’s Be Rehabilitated? A Program-by-Program, County-by-County Analysis,†Explorations in Economic History, 2003, 40 (3), 278–307.
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- Fite, Gilbert C., “Recent Progress in the Mechanization of Cotton Production in the United States,†Agricultural History, 1950, 24 (1), 19–28.
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- Fordson House, Serial numbers for assorted tractor models 2015. Available at: http://www. thefordsonhouse.com/.
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- Gilbert, C., An Economic Study of Farm Tractors in New York, Ithaca: Cornell University, 1930.
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- Griliches, Zvi, “Hybrid Corn: An Exploration in the Economics of Technological Change,†Econometrica, 1957, 25 (4), 501–522.
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- Gunlogson, G. B., “General Purpose Tractor Needed for American Farm Market,†Automotive Industries, 1922, 47.
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Hornbeck, Richard, “Barbed Wire: Property Rights and Agricultural Development,†The Quarterly Journal of Economics, 2010, 125 (2).
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Keller, Wolfgang, “Geographic Localization of International Technology Diffusion,†American Economic Review, 2002, 92 (1), 120–142.
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- Sanders, Ralph W., The Farm Tractor: 100 Years of North American Tractors, Minneapolis: Voyageur Press, 2009.
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- Soybeans were not grown in large quantity until the 1940s, when wartime foreign supply disruptions led to a dramatic expansion in domestic production, and are not included in these tables and figures.
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- State 1920 1930 1940 1920-30 1930-40 IA 991 981 931-0.01-0.05 IL 1107 1002 979-0.09-0.02 IN 914 815 816-0.11 0.00 KS 742 709 607-0.04-0.14 MI 856 785 871-0.08 0.11 MN 903 898 915-0.01 0.02 MO 1219 1118 1125-0.08 0.01 ND 398 398 328 0.00-0.18 NE 588 587 498 0.00-0.15 OH 1149 1016 1089-0.12 0.07 SD 364 391 307 0.07-0.21 WI 927 883 883-0.05 0.00 Notes: Table reports state farm population for Midwest states from 1920 to 1940, in thousands. Data from Historical Statistics of the U.S., Series Da28-92.
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- State 1940 1945 1950 1940-45 1945-50 IA 931 792 790-0.15 0.00 IL 979 759 773-0.22 0.02 IN 816 656 671-0.20 0.02 KS 607 480 445-0.21-0.07 MI 871 663 703-0.24 0.06 MN 915 731 746-0.20 0.02 MO 1125 855 869-0.24 0.02 ND 328 270 255-0.18-0.06 NE 498 404 393-0.19-0.03 OH 1089 842 870-0.23 0.03 SD 307 254 254-0.17 0.00 WI 883 720 733-0.18 0.02 Notes: Table reports state farm population for Midwest states from 1940 to 1950, in thousands. Data from 1950 Census of Agriculture. C Alternative Dependent Variables The specifications in the paper estimate linear models for the fraction of farms in a county reporting a tractor. This appendix repeats the exercise for alternative definitions of diffusion.
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Steckel, Richard H. and William J. White, “Engines of Growth: Farm Tractors and TwentiethCentury US Economic Welfare,†2012. NBER Working Paper 17879.
Suri, Tavneet, “Selection and Comparative Advantage in Technology Adoption,†Econometrica, 2011, 79 (1), 159–209.
- Table 1: Tractor Production from Select Manufacturers, Fixed Tread vs. General-Purpose Pre-study period Study Period Type 1917-1920 1921-1924 1925-1928 1929-1932 1933-1936 1937-1940 Fixed Tread 226,728 375,217 532,392 259,539 58,148 75,381 General-Purpose 0 214 50,884 125,577 260,626 524,666 Notes: Table shows total production of regular and general-purpose tractors by select manufacturers between 1917 and 1940. Sample covers production by Ford, IHC, Deere, and Allis-Chalmers, which account for 80% of tractors manufactured in each of the 1920s and 1930s (White 2010). Production totals calculated from manufacturer serial numbers, which were acquired from the McCormick collection at the Wisconsin Historical Society (IHC), thefordsonhouse.com (Ford), tractordata.com (Deere, Allis-Chalmers), and tractors.wikia.com (all).
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- Table 4: Crop Intensity and Changes in Tractor Diffusion from 1925 to 1940: Robustness to Alternative Specifications Additional controls for: Restricted to: Other Farm Financial Climate/ New Deal Dust Bowl Early Hybrid Baseline Pretrends Crop Mix Farm Size Characteristics Conditions Geography Relief Counties Corn Adopters (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) Panel A: Diffusion (levels) from 1925-1930 Pct. in Wheat 0.437*** 0.438*** 0.427*** 0.413*** 0.403*** 0.361*** 0.353*** x
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- Table 6: Crop Intensity and Changes in Tractor Diffusion from 1940 to 1950 Additional controls for: Restricted to: Other Farm Climate/ New Deal Dust Bowl Early Hybrid Baseline Pretrends Crop Mix Farm Size Characteristics Geography Relief Counties Corn Adopters (1) (2) (3) (4) (5) (6) (7) (8) (9) Diffusion (levels) from 1940-1950 Pct. in Wheat -0.278*** -0.277*** -0.210*** -0.254*** -0.206*** -0.210*** -0.097*** -0.133*** -0.059 x
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- Table 7: Tractor Diffusion by Region, from 1920 to Present Census Region 1920 1925 1930 1940 2002 Northeast 2.7 9.5 18.6 29.2 86.2 Midwest 6.8 13.6 25.7 42.4 89.6 South 1.0 2.3 4.0 7.9 91.8 excl. DE, MD, OK, TX 0.7 1.8 2.7 4.2 90.0 DE, MD alone 2.8 7.5 15.5 23.0 90.3 OK, TX alone 2.2 3.7 7.9 21.3 95.0 West 7.0 10.7 19.4 27.9 83.2 Notes: Table reports tractor diffusion by Census region in 1920, 1925, 1930, 1940, and 2002. The table highlights the lagging adoption of tractors in Southern states through 1940, especially those with historically poor labor institutions (slavery and sharecropping), and their eventual catch-up to the rest of the country.
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- Temporary National Economic Committee (TNEC) of the 76th U.S. Congress, Investigation of Concentration of Economic Power, Part 30: Technology and Concentration of Economic Power, Washington: GPO, 1940.
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- The data used in the New Deal and Dust Bowl robustness checks were obtained from Fishback, Kantor, and Wallis (2003) and Hornbeck (2012), respectively. The New Deal robustness checks include the Fishback et al. measures of AAA relief spending and FCA lending by county from 1933-1939, normalized by harvested acreage; the Dust Bowl robustness checks restrict to counties in the Hornbeck dataset, which are located in the Plains states (Kansas, Nebraska, the Dakotas, Iowa, and Minnesota) and were those most affected by the Dust Bowl. Hybrid corn diffusion was provided by Richard Sutch (Sutch 2011, 2014) and originally obtained from the USDA Agricultural Statistics; the hybrid corn adopter robustness checks are restricted to the six states that were leading adopters of hybrids (by a wide margin, see Table A.1) in 1940.
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- The latter two columns in Panel B retain the controls but restrict to counties in the Hornbeck (2012) Dust Bowl sample or to states that were leading adopters of hybrid seed corn to evaluate whether the effects are explained by contemporaneous shocks to Midwest agriculture in the 1930s. The difference in the diffusion rates to wheatvs. corn-intensive counties is provided below the regression estimates. *, **, *** represent significance at the 0.1, 0.05, and 0.01 levels, respectively. SEs clustered by county in parentheses.
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- The latter two columns in Panel B retain the controls but restrict to counties in the Hornbeck (2012) Dust Bowl sample or to states that were leading adopters of hybrid seed corn to evaluate whether the effects are explained by contemporaneous shocks to Midwest agriculture in the 1930s. The difference in the diffusion rates to wheatvs. corn-intensive counties is provided below the regression estimates. *, **, *** represent significance at the 0.1, 0.05, and 0.01 levels, respectively. SEs clustered by county in parentheses.
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- The latter two columns in Panel B retain the controls but restrict to counties in the Hornbeck (2012) Dust Bowl sample or to states that were leading adopters of hybrid seed corn to evaluate whether the effects are explained by contemporaneous shocks to Midwest agriculture in the 1930s. The difference in the diffusion rates to wheatvs. corn-intensive counties is provided below the regression estimates. *, **, *** represent significance at the 0.1, 0.05, and 0.01 levels, respectively. SEs clustered by county in parentheses.
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- The latter two columns in Panel B retain the controls but restrict to counties in the Hornbeck (2012) Dust Bowl sample or to states that were leading adopters of hybrid seed corn to evaluate whether the effects are explained by contemporaneous shocks to Midwest agriculture in the 1930s. The difference in the diffusion rates to wheatvs. corn-intensive counties is provided below the regression estimates. *, **, *** represent significance at the 0.1, 0.05, and 0.01 levels, respectively. SEs clustered by county in parentheses.
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- The latter two columns retain the controls but restrict to counties in the Hornbeck (2012) Dust Bowl sample or to states that were leading adopters of hybrid seed corn to evaluate whether the effects are explained by contemporaneous shocks to Midwest agriculture in the 1930s. The difference in the diffusion rates to wheatvs. corn-intensive counties is provided below the regression estimates. *, **, *** represent significance at the 0.1, 0.05, and 0.01 levels, respectively. SEs clustered by county in parentheses.
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- The next check replaces diffusion with the log-odds ratio: if diffusion follows a logistic pattern in the explanatory variables, then the log-odds ratio will be linear in these variables. Though Griliches (1957) demonstrates that diffusion follows a logistic pattern over time, it is not ex-ante obvious that it does so in other variables – but in the event that it does, the results in Table C.1 lay to rest any concerns that the results in the paper are driven by mismeasurement of the dependent variable, as the patterns persist for the log-odds measure.
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- The second table shows farm population in the 1940s, which declined precipitiously during World War II, mirroring the national trend. During the war, the Midwest farm population declined 21%, with state-level changes ranging from-15% in Iowa to-24% in Michigan. The proximate cause of the decline was the war effort, which mobilized adult males into other sectors: the 1950 Census of Agriculture notes that “a rapid loss of farm population occurred during World War II because of the demand for manpower in industry and in the military services.†Table B.2: Farm Population (thousands), State Totals, 1920-1940 Pct. Chg. Pct. Chg.
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- Tractor and Construction Plant Wiki, Serial numbers for assorted tractor models 2015. Available at: http://tractors.wikia.com/.
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- TractorData, Serial numbers for assorted tractor models 2015. Available at: http://www. tractordata.com/.
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- Tractors and implements (in millions) 0 10 20 30 Horses and mules (in millions) 1910 1920 1930 1940 1950 1960 Horses/mules All tractors All implements Notes: All implements refers to the sum of grain combines, corn harvesters, and pick-up hay balers owned by U.S. farms; this total does not include other implements not provided in the Historical Statistics or recorded in historical Censuses. Correlation of tractors and implements on U.S. farms is 0.996 over the 19 years for which data on all three implements are available. Data from Historical Statistics of the U.S., Series Da623, Da629-631, Da983, Da985, Da987.
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- U.S. Census Bureau, Census of Agriculture, Washington: GPO, 1910-1954.
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- U.S. Geological Survey, National Elevation Dataset 2009. Available at: http://ned.usgs.gov/.
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Whatley, Warren C., “A History of Mechanization in the Cotton South: The Institutional Hypothesis, †Quarterly Journal of Economics, 1985, 100 (4), 1191–1215.
- White, William J., “An Unsung Hero: The Tractor’s Contribution to Twentieth-Century United States Economic Growth,†2000. Unpublished dissertation.
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- Williams, Robert C., Fordson, Farmall, and Poppin’ Johnny: A History of the Farm Tractor and Its Impact on America, Urbana: University of Illinois Press, 1987.
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- Year=1930 (0.015) (0.021) (0.024) (0.026) (0.029) (0.029) (0.024) Difference -0.19*** -0.13*** -0.16*** -0.23*** -0.22*** -0.25*** -0.18*** s.e. (0.04) (0.05) (0.05) (0.05) (0.05) (0.05) (0.05) N 1470 1470 1470 1470 1470 1470 1470 R 2 0.40 0.40 0.54 0.70 0.74 0.74 0.80 Panel B: Diffusion (per 100 acres) from 1930-1940, excluding Plains states Pct. in Wheat -0.170*** -0.165*** -0.159*** -0.151*** -0.164*** -0.176*** -0.165*** -0.128*** -0.133*** -0.053 x
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- Year=1930 (0.020) (0.023) (0.023) (0.023) (0.023) (0.023) (0.023) Difference -0.42*** -0.40*** -0.42*** -0.39*** -0.38*** -0.31*** -0.30*** s.e. (0.04) (0.04) (0.04) (0.04) (0.04) (0.04) (0.04) N 2064 2064 2064 2064 2064 2064 2064 R 2 0.86 0.86 0.91 0.92 0.93 0.93 0.94 Panel B: Diffusion (levels) from 1930-1940 Pct. in Wheat 0.037 0.040 0.048 0.030 -0.033 -0.102*** -0.109*** -0.153*** -0.237*** -0.120* x
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- Year=1930 (0.020) (0.023) (0.023) (0.023) (0.024) (0.023) (0.023) Difference -0.42*** -0.40*** -0.42*** -0.39*** -0.38*** -0.31*** -0.30*** s.e. (0.04) (0.04) (0.04) (0.04) (0.04) (0.04) (0.04) N 2064 2064 2064 2064 2064 2064 2064 R 2 0.56 0.56 0.71 0.76 0.77 0.78 0.81 Panel B: Diffusion (levels) from 1930-1940 Pct. in Wheat 0.037 0.040 0.048 0.030 -0.033 -0.102*** -0.109*** -0.153*** -0.237*** -0.120* x
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- Year=1930 (0.028) (0.028) (0.030) (0.030) (0.029) (0.029) (0.028) Pct. in Corn 0.017 0.034 0.010 0.024 0.028 0.054*** 0.054*** x
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- Year=1930 (0.028) (0.028) (0.030) (0.030) (0.029) (0.029) (0.028) Pct. in Corn 0.017 0.034 0.010 0.024 0.028 0.054*** 0.054*** x
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- Year=1930 (0.030) (0.033) (0.034) (0.033) (0.033) (0.033) (0.032) Difference -0.42*** -0.40*** -0.42*** -0.39*** -0.38*** -0.31*** -0.30*** s.e. (0.05) (0.05) (0.06) (0.06) (0.05) (0.05) (0.05) N 2064 2064 2064 2064 2064 2064 2064 R 2 0.86 0.86 0.91 0.92 0.93 0.93 0.94 Panel B: Diffusion (levels) from 1930-1940 Pct. in Wheat 0.037 0.040 0.048 0.030 -0.033 -0.102** -0.109** -0.153*** -0.237*** -0.120 x
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- Year=1930 (0.039) (0.038) (0.043) (0.043) (0.039) (0.040) (0.039) Pct. in Corn 0.037*** 0.092*** 0.086*** 0.037 0.036 0.028 0.053** x
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- Year=1930 (0.039) (0.039) (0.044) (0.042) (0.041) (0.040) (0.038) Pct. in Corn 0.017 0.034 0.010 0.024 0.028 0.054 0.054* x
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- Year=1930 (0.045) (0.049) (0.050) (0.049) (0.049) (0.047) (0.047) Difference -0.42*** -0.40*** -0.42*** -0.39*** -0.38*** -0.31*** -0.30*** s.e. (0.08) (0.08) (0.09) (0.09) (0.08) (0.08) (0.07) N 2064 2064 2064 2064 2064 2064 2064 R 2 0.86 0.86 0.91 0.92 0.93 0.93 0.94 Panel B: Diffusion (levels) from 1930-1940 Pct. in Wheat 0.037 0.040 0.048 0.030 -0.033 -0.102 -0.109 -0.153* -0.237*** -0.120 x
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- Year=1930 (0.056) (0.056) (0.064) (0.060) (0.057) (0.055) (0.052) Pct. in Corn 0.017 0.034 0.010 0.024 0.028 0.054 0.054 x
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- Year=1930 (0.091) (0.109) (0.118) (0.125) (0.144) (0.143) (0.134) Difference -1.22*** -1.24*** -1.38*** -1.18*** -1.15*** -0.62*** -0.67*** s.e. (0.16) (0.17) (0.19) (0.19) (0.20) (0.20) (0.20) N 2064 2064 2064 2064 2064 2064 2064 R 2 0.60 0.60 0.71 0.77 0.78 0.80 0.83 Panel B: Diffusion (log-odds) from 1930-1940 Pct. in Wheat -0.515*** -0.515*** -0.482*** -0.570*** -0.668*** -1.205*** -1.154*** -1.479*** -1.232*** -1.168*** x
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- Year=1930 (0.130) (0.130) (0.149) (0.146) (0.180) (0.176) (0.157) Pct. in Corn -0.400*** -0.426*** -0.579*** -0.440*** -0.345*** -0.240* -0.252* x
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- Year=1940 (0.020) (0.019) (0.022) (0.022) (0.024) (0.025) (0.024) (0.028) (0.031) (0.061) Pct. in Corn 0.213*** 0.281*** 0.383*** 0.401*** 0.367*** 0.395*** 0.316*** 0.352*** 0.317*** 0.068 x
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- Year=1940 (0.020) (0.027) (0.034) (0.030) (0.039) (0.038) (0.039) (0.041) (0.040) (0.069) Difference 0.38*** 0.45*** 0.54*** 0.55*** 0.53*** 0.57*** 0.48*** 0.48*** 0.45*** 0.12 s.e. (0.02) (0.03) (0.04) (0.04) (0.04) (0.04) (0.04) (0.04) (0.03) (0.08) N 1884 1884 1884 1884 1884 1884 1884 1884 874 986 R 2 0.50 0.50 0.62 0.74 0.79 0.80 0.84 0.84 0.88 0.86 Notes: Table shows the relationship between pre-period crop intensity and changes in county-level tractors per hundred farm acres from 1925-30 and 1930-40 (Panels A and B, respectively). Column (1) repeats the baseline estimates from Table 3, and the remaining columns provide robustness checks.
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- Year=1940 (0.021) (0.025) (0.037) (0.035) (0.042) (0.038) (0.036) (0.042) (0.059) (0.063) Difference 0.38*** 0.41*** 0.50*** 0.50*** 0.42*** 0.53*** 0.48*** 0.49*** 0.46*** 0.27*** s.e. (0.04) (0.04) (0.06) (0.05) (0.05) (0.05) (0.05) (0.05) (0.06) (0.10) N 1884 1884 1884 1884 1884 1884 1884 1884 874 986 R 2 0.61 0.61 0.73 0.79 0.81 0.83 0.86 0.86 0.84 0.88 Notes: Table shows the relationship between pre-period crop intensity and changes in county-level tractor diffusion from 1925-30 and 1930-40 (Panels A and B, respectively). Column (1) repeats the baseline estimates from Table 3, and the remaining columns provide robustness checks.
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- Year=1940 (0.022) (0.025) (0.037) (0.035) (0.042) (0.039) (0.036) (0.042) (0.058) (0.062) Difference 0.38*** 0.41*** 0.50*** 0.50*** 0.42*** 0.53*** 0.48*** 0.49*** 0.46*** 0.27*** s.e. (0.04) (0.04) (0.06) (0.05) (0.05) (0.05) (0.05) (0.05) (0.06) (0.10) N 1884 1884 1884 1884 1884 1884 1884 1884 874 986 R 2 0.91 0.91 0.94 0.95 0.96 0.96 0.97 0.97 0.98 0.98 Notes: Table shows the estimates from Table 4 in the paper with Conley (1999) standard errors, which allow for spatial correlation in the error term that declines linearly in distance up to a fixed cutoff point. The difference in the diffusion rates to wheatvs. corn-intensive counties is provided below the regression estimates. *, **, *** represent significance at the 0.1, 0.05, and 0.01 levels, respectively. Conley SEs in parentheses.
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- Year=1940 (0.030) (0.030) (0.037) (0.036) (0.034) (0.035) (0.034) (0.040) (0.050) (0.069) Pct. in Corn 0.413*** 0.450*** 0.543*** 0.532*** 0.384*** 0.425*** 0.373*** 0.333*** 0.221*** 0.145*** x
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- Year=1940 (0.030) (0.030) (0.037) (0.036) (0.034) (0.035) (0.034) (0.040) (0.051) (0.070) Pct. in Corn 0.413*** 0.450*** 0.543*** 0.532*** 0.384*** 0.425*** 0.373*** 0.333*** 0.221*** 0.145** x
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- Year=1940 (0.033) (0.037) (0.056) (0.052) (0.056) (0.051) (0.047) (0.052) (0.068) (0.074) Difference 0.38*** 0.41*** 0.50*** 0.50*** 0.42*** 0.53*** 0.48*** 0.49*** 0.46*** 0.27** s.e. (0.06) (0.06) (0.09) (0.08) (0.07) (0.07) (0.07) (0.07) (0.08) (0.13) N 1884 1884 1884 1884 1884 1884 1884 1884 874 986 R 2 0.91 0.91 0.94 0.95 0.96 0.96 0.97 0.97 0.98 0.98 Notes: Table shows the estimates from Table 4 in the paper with Conley (1999) standard errors, which allow for spatial correlation in the error term that declines linearly in distance up to a fixed cutoff point. The difference in the diffusion rates to wheatvs. corn-intensive counties is provided below the regression estimates. *, **, *** represent significance at the 0.1, 0.05, and 0.01 levels, respectively. Conley SEs in parentheses.
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- Year=1940 (0.045) (0.045) (0.055) (0.053) (0.049) (0.050) (0.049) (0.056) (0.066) (0.099) Pct. in Corn 0.413*** 0.450*** 0.543*** 0.532*** 0.384*** 0.425*** 0.373*** 0.333*** 0.221*** 0.145* x
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- Year=1940 (0.065) (0.066) (0.081) (0.077) (0.071) (0.071) (0.069) (0.079) (0.088) (0.132) Pct. in Corn 0.413*** 0.450*** 0.543*** 0.532*** 0.384*** 0.425*** 0.373*** 0.333*** 0.221*** 0.145* x
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- Year=1940 (0.094) (0.110) (0.169) (0.168) (0.218) (0.203) (0.188) (0.218) (0.279) (0.316) Difference 1.88*** 1.88*** 2.42*** 2.44*** 2.30*** 3.07*** 2.89*** 2.89*** 1.93*** 1.69*** s.e. (0.14) (0.15) (0.23) (0.22) (0.23) (0.22) (0.22) (0.22) (0.26) (0.48) N 1884 1884 1884 1884 1884 1884 1884 1884 874 986 R 2 0.62 0.62 0.73 0.80 0.82 0.84 0.86 0.86 0.84 0.88 Notes: Table shows the relationship between pre-period crop intensity and changes in the log-odds ratio of county-level tractor diffusion from 1925-30 and 1930-40 (Panels A and B, respectively). Column (1) repeats the baseline estimates from Table 3, and the remaining columns provide robustness checks.
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- Year=1940 (0.117) (0.117) (0.142) (0.146) (0.145) (0.164) (0.160) (0.197) (0.233) (0.330) Pct. in Corn 1.359*** 1.367*** 1.933*** 1.870*** 1.629*** 1.862*** 1.735*** 1.407*** 0.695*** 0.525* x
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- Year=1950 (0.029) (0.031) (0.035) (0.035) (0.040) (0.041) (0.044) (0.055) (0.059) N 1886 1886 1886 1886 1886 1886 1886 876 986 R 2 0.74 0.74 0.82 0.87 0.88 0.89 0.90 0.86 0.91 Notes: Table shows the relationship between pre-period crop intensity and changes in county-level tractor diffusion from 1940-50. Column (1) runs the baseline specification without controls, and the remaining columns provide robustness checks.
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- Year=1950 (0.034) (0.034) (0.036) (0.035) (0.036) (0.036) (0.037) (0.048) (0.064) Pct. in Corn -0.358*** -0.341*** -0.382*** -0.341*** -0.408*** -0.360*** -0.268*** -0.232*** -0.470*** x
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