Two econometric issues arise in the estimation of complete systems of producer or consumer demands when many non-negativity constraints are binding for a large share of observations, as frequently occurs with micro-level data. The first is computational. The econometric model is essentially an...

The Impact of Microcredit on the Poor in Bangladesh: Revisiting the Evidence,' by David Roodman and Jonathan Morduch (2014) is the most recent of a sequence of papers and postings that seeks to refute the findings of the Pitt and Khandker (1998) article 'The Impact of Group-Based Credit on Poor...