If the article includes several estimated effects, the intent-to-treat parameter is the preferred estimate (Croke et al. 2016). The intent-to-treat parameter is the estimated effect of participating in the subsidy program (i.e. receiving vouchers/cash) on yield or income, and not the effect on people who actually buy subsidized inputs with the vouchers. Ideally, the parameters in the meta-analysis would come from randomized trials, which is the gold standard for program evaluation, but there are few such studies, so we also include quasi-experimental studies in this meta-analysis. We examine the relationship between experimental estimates and effect size for robustness in Section 3.3.

# **3. Results**

# **3.1 Sample characteristics**

A description of the 39 articles at the full text screening stage is included in Table 1. The top three reasons for exclusion at the abstract screening stage were “Not an input subsidy or price intervention” (199 articles), “Not a low- or middle-income country” (82 articles), and “Not related to agriculture” (39 articles). At the full-text screening stage, the top three reasons for exclusion were “Non-causal method” (11 articles), “Not impact on output, yield, or income” (8 articles), and “Non-original research or review article” (5 articles). Of the 39 articles, 28 examine countries in Sub-Saharan Africa, and the final metaanalysis sample includes 11 articles with data from Sub-Saharan countries and 1 from a non-African country (China). Our primary outcome of interest, productivity, is examined in 21 of the 39 articles, and 11 of them are included in the meta-analysis. Our secondary outcome of interest, income or expenditure, is studied in 8 articles, and 7 are included in the meta-analysis.

The methods used to analyze program impact varies in the articles we have identified. Studies using non-causal and non-quantitative methods are excluded. Some studies employ multiple methods to show robustness and estimate several treatment effects. Whenever possible, we use the intent-to-treat estimate (Croke et al. 2016). All 3 studies that conducted randomized trials are included in the metaanalysis. Most studies that use instrumental variable (IV), propensity score matching, and difference-indifferences are included in the meta-analysis. The meta-analysis includes 3 papers using IV, 5 papers using propensity score matching, 1 paper using difference-in-differences, and 3 papers using fixed effects. Of the 13 studies that use other quantitative methods, 4 are included in the meta-analysis.

The articles at the full text screening stage vary in program characteristics. Of the 39 articles we have identified, 16 studies examine programs that provide a full subsidy (free distribution) of fertilizer and improved seeds, while another 16 examine programs that provide partial subsidies. The remaining 7 are excluded because the interventions do not include input subsidies. Among the 12 studies included in the meta-analysis, 7 of them examine a full subsidy program and 5 examine a partial subsidy program where the subsidies range from 50% to 93%. In terms of the distribution mechanism, 26 studies examine programs that use vouchers, including e-vouchers, and 4 studies examine programs that use cash transfers. Eleven studies that examine voucher programs and one study that examines a cash transfer program are included in the meta-analysis. The cash transfer study (Yi, Lu, and Zhou 2016) analyzes a program that provided direct payments and input subsidy to grain producers in China. The subsidy to an average household is approximately 2 percent of its total income, or about 5 percent of its agricultural 6