The study found that the empirical evidence is limited to the analysis of mainly three standards: GlobalGAP, fair trade and organic. Moreover, most studies focus on two commodities: coffee and horticulture products. While there is a decent range of geographic cover, the majority of studies focus on a handful of countries: Mexico, Kenya, Peru, Costa Rica and Uganda. This study adopts an impacts pathway model to organize and analyze the trends found in the empirical evidence. The results can be summarized as follows: first, equitable and sustainable supply chain linkages, increased access to assets, and support for cooperative development are incentives for complying with standards. Second, both public and private actors have comparative advantages for supporting voluntary standards and are most effective when combined. Finally, governments can provide services, for example infrastructure and proper legislation, that facilitate the inclusion of smallholders in certified value chains. The study concludes by making policy recommendations on how the public sector can mediate the effects of voluntary standards.--