Here are a few details about the person who made the brocade dog collar you might have bought on Etsy : She has a college degree, she probably used her savings to start her online shop and most of her household’s income comes from other sources.

And, she is almost definitely a she—86% of the site’s sellers are female.

The data comes from a report out Thursday from the online handmade-goods marketplace, one of the earliest platforms allowing for a certain kind of microcommerce: people transacting with each other through a website or app, with limited involvement from the marketplace. Think eBay Inc., Airbnb, Uber Technologies Inc. and TaskRabbit.

Brooklyn, N.Y.-based Etsy Inc. found that about 30% of its sellers use their creative business as their sole source of earnings. For the rest, sales offer supplemental income, another feature of the app economy—it has allowed perhaps millions of Americans to find fractional employment, in which people earn extra money if and when they need it.

“The workforce is shifting away from full-time employment, and more and more people are combining income from multiple sources,” said Althea Erickson, Etsy’s global policy director. Etsy sellers have median household incomes of $56,180, slightly above that of the general population, with Etsy income contributing an average of 15% of the total. “Supplemental income really matters,” said Ms. Erickson.