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2021.11/2022.03改訂

This dissertation consists of three essays empirically investigating three important aspects of the U.S. agriculture: conservation, subsidy, and productivity. Each essay is conducted with the U.S. Census of Agriculture micro file data. Availability of cross-sectional and time variations of detailed individual farm production and demographic characteristics allows for uncovering heterogeneous relationships between farm production decisions and the corresponding aspects of U.S. agriculture. The first essay examines an adverse effect of a cropland retirement policy. A cropland retirement policy contributes to the reduction of environmental externalities from agricultural production such as soil erosion, nutrient runoff and loss of wildlife habitat. On the other hand, participant's potential adverse behavior could undermine the environmental benefits of the policy. Several sources of such an unintended effect, known as ``slippage'', have been conceptually identified, but their empirical evidence has been scarce. This article tests one source of slippage caused by in-farm land substitution from noncropland to cropland as a result of farmland retirement in the U.S. Conservation Reserve Program (CRP). The causal relationship of CRP participation and subsequent slippage through in-farm land substitution is identified by employing farm fixed effects, time-varying county fixed effects, and selection-on-observables. These could eliminate effects of unobservables that are potentially correlated with both the program participation and subsequent farmland reallocation decisions. Overall, slippage seems evident and fairly robust among specifications. It is found that an average program participant converts 14% of noncropland to cropping activities after enrollment. Results further show that participants with a larger share of uncropped land contribute more to slippage, indicating that farms with the excess capacity of conversion are more flexible in the land allocation decision and thus likely to give rise to slippage. This suggests that additional restrictions on the rest of land use for participants and/or introduction of penalty points reflecting the share of noncropland in the current auction mechanism can hinder such a backward incentive offsetting the program benefits. The second essay examines the distortionary effects of agricultural policy on farm productivity by examining the response of U.S. tobacco farmers' productivity to the quota buyout of 2004. We focus on the impact of distortionary policy, i.e., the tobacco quota, by decomposing aggregate productivity growth into the contribution of farm-level productivity growth and the contribution of reallocation of resources among tobacco growers. We find that the aggregate productivity of Kentucky tobacco farms grew 44% between 2002 and 2007. The elimination of quota rental costs and reallocation of resources, including entry and exit, accounted for most of the post-buyout productivity growth. It is also noted that the aggregate productivity of Kentucky tobacco farms vary across farm characteristics and locations. This highlights the importance of using highly disaggregated data to uncover the sources of aggregate productivity growth. The third essay examines the relationship between farm size and productivity growth. In the past several decades, crop production in the U.S. has shifted to larger farms. During the same period, crop productivity has fairly improved. While these two events seem clearly associated, no studies have fully uncovered the link between them. Using farm-level longitudinal data from the Censuses of Agriculture from 1987-2007 enables us to decompose aggregate productivity growth (APG) by farm size, but also by farm entry/exit and by technology/reallocation. We have three main findings. First, productivity growth is clearly non-uniform among farm sizes. Between 1987 and 2007, virtually all of the aggregate productivity growth of crop farms came from farms with annual sales of more than $500,000. These farms account for only 8% of U.S. crop farms. A closer look at the APG contributions to productivity growth from surviving farms confirms the findings for all crop farms: the productivity of mid-size farms has barely increased, and the productivity of smaller farms has fallen. Finally, the relative importance of technical efficiency growth and resource reallocation varies over time. Technical efficiency growth seems to be a larger source of APG for large farms between 1987 and 1997, whereas reallocation across all sales classes contributes more to APG between 1997 and 2007. Overall, our finding provides the concrete evidence that farm consolidation has been strongly associated with the productivity growth of U.S. crop farms. Our finding that resource reallocation through farm consolidation is nontrivial for the APG of crop farms highlights the usefulness of farm-level panel data for studying structural changes and APG.

A cropland retirement policy contributes to the reduction of environmental externalities from agricultural production such as soil erosion, nutrient runoff and loss of wildlife habitat. On the other hand, participant's potential adverse behavior could undermine the environmental benefits of the policy. Several sources of such an unintended effect, known as “slippage", have been conceptually identified, but their empirical evidence has been scarce. This article tests one source of slippage caused by in-farm land substitution from noncropland to cropland as a result of farmland retirement in the U.S. Conservation Reserve Program (CRP). With the farm-level longitudinal data I can utilize cross-sectional and time variation of detailed individual farm characteristics to identify the causal relationship of CRP participation and subsequent slippage through in-farm land substitution. An identified assumption of the slippage estimate is verified by farm fixed effects, time-varying county fixed effects, and selection-on-observables. These could eliminate effects of unobservables that are potentially correlated with both the program participation and subsequent farmland reallocation decisions. Overall, slippage seems evident and fairly robust among specifications. It is found that an average program participant converts 14% of noncropland to cropping activities after enrollment. Results further show that participants with a larger share of uncropped land contribute more to slippage, indicating that farms with the excess capacity of conversion are more exible in the land allocation decision and thus likely to give rise to slippage. This suggests that additional restrictions on the rest of land use for participants and/or introduction of penalty points reecting the share of noncropland in the current auction mechanism can hinder such a backward incentive offsetting the program benefits.

Among multiple slippage effects potentially generated in voluntary land retirement programs, this study attempts to identify one unique source of slippage. Specifically, I examine slippage caused by within-a-farm land conversion from uncultivated land to cropland. With the U.S. Agricultural Census farm-level longitudinal data on land use and enrollment in the Conservation Reserve Program (CRP), I find that an average partial-farm CRP participant converts 25% of noncropland to cropping activities as a consequence of CRP enrollment. Also, an estimated slippage rate varies across farm types and regions. In particular, farms with relatively inelastic crop acreage supply lead to more slippage. Knowledge about the mechanisms through which slippage occurs should help policymakers devise programs with features designed to avoid or mitigate slippage incentives.

Under the Clean Development Mechanism (CDM) of the Kyoto Protocol, forest projects can receive returns for carbon sequestration via two credit instruments: temporary (tCERs) or long-term certified emission reductions (lCERs). This article develops a theoretical model of optimal harvesting strategies that compares private optimal harvest decision under these two instruments. We find that risk neutral landowners are likely to prefer instituting lCERs over tCERs to maximize surplus. A particular type of early harvest penalty implemented under the lCERs is critical in determining the length of rotation intervals and the carbon credit supply. When this penalty is an increasing function of the difference in biomass before and after harvesting across verification periods, the landowner may choose longer or shorter rotation intervals compared to the Faustmann rotation. The resulting supply curve may have a backward bending region over a range of carbon prices.

We examine the distortionary effects of agricultural policy on farm productivity by examining the response of U.S. tobacco farmers' productivity to the quota buyout of 2004. We isolate the impact of distortionary policy, i.e., the tobacco quota, by decomposing aggregate productivity growth into the contribution of farm-level productivity growth and the contribution of reallocation of resources among tobacco growers. Reallocation of resources includes entry into and exit from tobacco farming, as well as growth or decline of the resources allocated to existing tobacco farms. We find that aggregate productivity of Kentucky tobacco farms grew 37% between 2002 and 2007. Reallocation of resources among continuing tobacco farms contributed 22 percentage points to productivity growth. Reallocation through entry and exit contributed 10 percentage points, and the elimination of quota rental costs directly contributed 5 percentage points.