R Karina Gallardo och Johannes Sauer ger i en artikel i Annual Review of Resource Economics 2018 en översikt över arbetsbesparande innovationer i jordbruket. Så här USA-centrerat börjar deras historiska sektion:
"In the post–World War II era in the United States, farm labor declined by at least two-thirds, and the ratio of machinery to labor doubled. The prevailing view was that obstacles to migration out of agriculture depressed rural wages, inducing farmers to substitute capital and intermediate inputs for cheap labor (Rosenzweig 1988). In fact, Manuelli & Seshadri (2014) provided evidence on the impact of low labor costs on the slow rate of tractor adoption in US agriculture between 1910 and 1940." (s. 186)
Herrendorf et al (2015) menar att labor-augmenting teknologiska framsteg efter 1945 skedde snabbare i jordbruket än i industrin eller tjänsterna i USA:s ekonomi. Alvarez-Cuadrado et al (2017) visar att jordbruket blev relativt oviktigt för sysselsättningen genom att bli mer kapitalintensivt jämfört med resten av ekonomin. Hur lämnade arbetskraften jordbruket, var det push-faktorer eller pull-faktorer som var viktigast?
"Technological changes in agriculture have also led to studies of labor pull or push. LaborJordbruket i USA är beroende av invandring: 75 procent av lantarbetarna i USA idag kommer från Mexiko. Detta beror både på svag ekonomisk utveckling i Mexiko sedan 1994, relativt bra utveckling i USA med många andra jobb tillgängliga, och stora vatten-infrastrukturinvesteringar i västra USA under 1900-talets första hälft som stimulerade tillväxten av riktigt stora gårdar.
pull suggests that capital accumulation raised urban wages and attracted surplus labor out of the agricultural sector (Gylfason & Zoega 2006), whereas Peterson & Kislev (1986) concluded that technological change in agriculture induced labor to be pushed in rather than pulled out of the sector. However, Alvarez-Cuadrado & Poschke (2011) concluded that both the pull and push phenomena occurred at different periods in time. Improvements in industrial technology pulled labor out of agriculture until the 1920s; after 1960, improvements in agricultural technology pushed resources into agriculture." (s. 187)
De ekonomiska teorierna om arbetsbesparande teknologisk förändring börjar med John Hicks The Theory of Wages (1932) där Hicks lade fram "induced innovation theory". Forskare inom jordbruksekonomi modellerar jordbrukarens val att investera i teknologi, kontra att anställa fler arebtare, på olika sätt: ex ante-modeller som net present value (NPV) och ex post-modeller som diffusion models som den S-formade kurvan som diskuteras också i Manuelli och Seshadris traktorpapper. I ex post-kategorin ingår också tröskel-modellerna:
"David (1969) developed the threshold model, in which heterogeneity in the population of potential adopters was critical to the adoption decision. David & Olsen (1984, 1986) introduced the concept of “capital-using automation of production methods” in the transition to the new technology. This generalized approach also introduced the concept of a “learning process,” in which the novel capital good could be improved over time, and these improvements would be based on accumulating experience and would reduce the cost of the innovation.För de stora innovationerna som sparat arbete inom åkerbruket, börjar Gallardo och Sauers diskussion så här:
Threshold models vary in their analysis of adoption by individual decision makers. Several models use static models emphasizing risk considerations (e.g., Jensen 1982), whereas others use dynamic models. McWilliams & Zilberman (1996) determine the timing of adoption using the trade-off between the gain from early adoption versus the decreased fixed cost of the technology by delay. The literature suggests that dynamic processes resulting in changes in key variables have higher explanatory power compared to static approaches (Feder et al. 1985, Karshenas & Stoneman 1993, Sunding & Zilberman 2001, Koundouri et al. 2006)." (s. 190)
"Labor-saving mechanization has been successful in the agricultural crop industry since the 1800s. During that century, three major labor-saving machines were developed: John Deere’s steel plow, Cyrus McCormick’s reaper, and John Appleby’s grain binder. Early in the 1900s, gasoline engines were adapted to existing machines, and a wide variety of mass-production harvesting machines became available, including the self-propelled wheat combine, the hay baler, and cotton and corn pickers. By the 1960s, grains and almost all roots and tubers were harvested entirely through mechanized methods (Kelly 1967). Tractors, combines, and other farm machinery were continuously improved during the second half of the twentieth century to maximize efficiency, productivity, and ease of use (Edan et al. 2009)." (s. 191)
Det andra teknologiska fält som de diskuterar är bevattningen. Det tredje är seedling production, och det fjärde är automatiserade besprutare. Det femte är arbetet mot skadedjur, och det sjätte skörde-arbetet. Då här börjar diskussionen i den sektionen:
"Crop harvesting machines date from the eighteenth century with the invention of the cotton gin by Eli Whitney. In the 1920s, the Rust brothers developed a cotton picker prototype that was successfully adopted along with an improved cotton cultivar more adaptable to the machine (Kelly 1967). Another widely adopted mechanical harvester device was the tomato harvester that was facilitated by the confluence of several disciplines, including plant breeding, horticulture, and engineering (Rasmussen 1968). The tomato harvester led to cost savings of 40% compared to hand harvesting (Rasmussen 1968, Schmitz & Seckler 1970). Despite positive net gains to society, the tomato harvester led to labor displacements affecting vulnerable farm workers (Schmitz & Seckler 1970). Increased industry concentration was suggested as a solution, as greater initial capital investments were required to purchase the harvester compared to manual labor. In addition, larger operations consisting of more cultivated area were more likely to gain efficiencies because they could use the harvester to its fullest capacity (Rasmussen 1968). Early attempts to mechanically harvest fruits included the development of tree shakers, in which the movement detached fruit from the tree without damaging the tree, and catching devices that would prevent damage to the fruit. These machines proved successful in harvesting deciduous fruit trees with robust trunks and fruit surfaces that could withstand impact—such as plums—and for fruits destined for the processing market but not the fresh market, such as apples, cherries, or peaches (Karkee et al. 2017)." (s. 194)
Inom djurhållningen pekar de först på 1950-talets genomslag i avel. På 1970-talet började dual purpose cows (alltså både köttdjur och mjölkkor på samma gång) ersättas av rena mjölkdjur, framför allt Holstein-Friesian. Samtidigt började man mekanisera djurskötseln; den viktigaste innovationen var mjölkningsmaskinen. (s. 195) Att lönerna steg på 1970-talet var en viktig orsak till den ökade mekaniseringen inom mjölkning. (s. 196)
referens
R Karina Gallardo och Johannes Sauer, "Adoption of labor-saving technologies in agriculture", Annual Review of Resource Economics 2018.
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