“…The farm fixed effect controls for any farm characteristics that cannot be observed, such as landscapes with different agro-climatic conditions, do not change over time and that may influence farm production outcomes. The inclusion of the year fixed effect, ψ t , in Equation (1), is to control for shocks common to all the farms, for example, changes in market signals to all farms and price volatility [55,56]. Several factors confound the identification of the causal impact of decoupled payments on farm-level production [13,14,19].…”