Consumers who pay extra for coffee or other products with Fairtrade labels may not be helping the lives of the world’s poor, a new study suggests. Researchers from SOAS, University of Londonm spent four years looking at coffee, tea and flower workers in Ethiopia and Uganda. The study finds some at Fairtrade sites earning less than those at workplaces that are not Fairtrade certified.

Fairtrade International, which sets standards, is pushing back, saying the study makes unfair comparisons, though CEO Harriet Lamb does says the study makes valid points about the challenge of making sure Fairtrade money flows all the way through farmers to farm hands.

Christopher Cramer, one of the study’s authors, says Fairtrade does do good. He and his colleagues would like to see consumers get “clearer information about exactly who benefits and how and on the basis of what evidence.”

The conversation the study is provoking about Fairtrade is a reminder for anyone who shops with an eye toward a certain goal, be that supporting local, organic or Fairtrade producers. It’s wise to do a bit of homework to make sure that extra money is doing what is hoped.