It would be easy to see this as the normal trial-and-error of young people starting out careers, but actually the factory jobs carried dangerous risks. Serious injuries and disabilities were nearly double among those who took the factory jobs, rising to 7 percent from about 4 percent. This risk rose with every month they stayed. The people we interviewed told us about exposure to chemical fumes and repetitive stress injuries.

Why were people lining up for hazardous jobs? Partly it was because they did not appreciate the risks, or how hard the work was, until they started. Others anticipated the risks but used factory work as a safety net when times were tough. The people who stayed longer had few alternatives.

We have to be careful about generalizing from five businesses in one country, but this study has still shaped our views of factory work. Industrialization is not a quick fix. The first defense of industry probably still holds: Over time, a booming sector tends to improve labor conditions and bid up wages as more businesses compete for workers. But the path there isn’t smooth. In the short run workers seem to share few of the benefits but a heavy burden of the risks — a burden borne by the desperate and the uninformed.

We did not test solutions, but history and our experiences give us ideas.

One unexpected lesson is that companies need better middle management. The factory owners and investors told us that high turnover was their biggest concern and that finding good managers to reduce it was their biggest headache. We had the same impression of managers, especially when our study seemed to bring more organization to the hiring process than the companies had seen before. Collecting the names of all applicants, doing a basic screening, briefing people on the job and wages — these were all new to most of the managers we met.

History tells us to expect management practices and working conditions to improve over time. High employee turnover was certainly costly in the United States and Europe a century ago. In 1913, the Ford Motor Company recorded turnover rates of over 300 percent. Pay was poor and the work hard, and workers left in droves. Many of the modern management strategies we think are about factory efficiency started as attempts to lower this turnover. Eventually they helped make these companies better workplaces. “Better human resource management” is not the sexiest economic development strategy, but it is definitely an effective one.

A second possible solution is social welfare systems and safety nets. With those, desperate people are not forced to risk their health at poorly managed factories. An aspect of our study put this idea to the test. We offered some applicants who did not get the factory job a business start-up package of training and cash. Those people expanded their agricultural or market selling, raised their earnings by a third and did not feel the need to resort to factory jobs. Like other poor countries, Ethiopia is experimenting with various social insurance schemes. That should continue.