Students who attended for-profit private colleges in the United States to learn a trade saw their earnings drop. The report by the National Bureau of Economic Research said, on average, people who attended for-profit colleges made $920 less per year after they left school compared to before they started. People who attended public two-year colleges earned about $1,500 more per year than they did before starting their studies, the report said. And, the report noted that about nine out of 10 students borrowed money to attend for-profit colleges. The average debt for people attending two-year for-profit colleges was $8,000, according to the report. The report looked at schools preparing students for a number of trades, including health-care assistant, dental assistant, auto mechanic and cosmetologist. A cosmetologist works in a hair salon, cutting hair and creating styles for customers. Among the vocational trades examined by the research, only cosmetology programs appear to bring better pay in the for-profit sector, the report said. But overall, researchers found that many students who attended for-profit schools were worse off financially than they were before going to these colleges.