世界银行-化肥进口禁令、农产品出口和福利：来自斯里兰卡的证据（英）-2023.12-84页_9mb

Summary of "Fertilizer Import Bans, Agricultural Exports, and Welfare: Evidence from Sri Lanka"

Introduction

This study quantifies the economic impact of a sudden and unexpected fertilizer import ban in Sri Lanka (May 2021). Using a natural experiment—unprecedented in its abruptness and economy-wide effects—the research combines high-frequency trade data, agricultural production data, and remote sensing techniques. The goal is to assess the value of fertilizer in agriculture, particularly relevant for policy debates on subsidies and environmental regulations. Sri Lanka's economy is heavily reliant on agriculture, making this analysis timely given global fertilizer shortages and environmental concerns.

Methodology

The study employs a dynamic difference-in-differences approach to analyze import, production, and export data, complemented by novel remote sensing data for crop yields. A quantitative spatial model of trade and agriculture is developed, incorporating heterogeneous crop production technologies and geographic variations in land inequality. The model is calibrated using rich datasets, including customs trade records, government agricultural statistics, household surveys, and satellite imagery.

Key Data Sources:

• Trade Data: High-frequency firm- and product-level data from Panjiva for 2017–2022.
• Production/Remote Sensing: Remote sensing from satellite imagery provides detailed rice yield and cultivation area data.
• Household Polls: Data from Sri Lanka's Household Income and Expenditure Survey to inform preferences and labor distribution.
• Input-Output Matrix: Data on fertilizer and crop inputs to estimate production technology.

The model calculates welfare effects, decomposing impacts into price and quantity changes, and estimates the general equilibrium effects of reduced fertilizer access.

Key Findings

Before the Ban

• Sri Lanka’s economy in 2019–2020 was largely dependent on chemical fertilizers.
• Fertilizer prices were stable before the ban but surged post-ban due to import restrictions.

Reduced Fertilizer Imports

• After the ban, fertilizer imports decreased by approximately 99% from their pre-ban levels, as bans were lifted inconsistently.

Decline in Agricultural Production

• Remote sensing revealed a 32% drop in rice yields post-ban, with significant regional heterogeneity, particularly in high-yield producing districts.

Impact on Exports

• Agricultural exports fell overall by 5.5%, with exports from fertilizer-intensive products (e.g., rice and potatoes) declining disproportionately—potatoes fell by 14.3%.

Welfare Effects

• Average income loss in the economy was equivalent to 1.5% due to lack of fertilizer access.
• Welfare losses were concentrated on landowners (whose income is tied to agriculture) versus more mobile workers, with variations by district.

Spatial Heterogeneity

• Welfare losses varied significantly by region. Landowners in districts with high shares of fertilizer-intensive crops (e.g., rice) faced up to 6% income losses, while workers suffered less in areas with stronger manufacturing sectors.

Conclusion

This study provides a rigorous quantitative assessment of the value of fertilizers to agricultural production and trade in a developing economy. Key takeaways:

• Economic Value: The ban led to substantial welfare losses, confirming the importance of fertilizer.
• Policy Implications: Findings inform policy discussions on fertilizer subsidies versus environmental regulations.
• Robustness: Results withstand placebo tests and external factor controls.

The welfare analysis yields valuable insights into income distribution effects of agricultural policies.