The share of young men making between $30,000 and $100,000 a year shrank significantly over the past four decades, despite the fact that they are better educated and working full time at the same rate. Many of them have fallen to the bottom of the income scale, according to a new analysisby the US Census Bureau, and this shift is having a major impact on the rest of their lives.

The loss of blue-collar jobs, many of which are now performed by machines or by workers overseas, is forcing more men into low-wage service jobs, and in some cases causing them to drop out of the workforce altogether…

In Massachusetts, the high school graduation rate is 85 percent for boys and 90 percent for girls; the six-year completion rate at public colleges is 63 percent for women and less than 58 percent for men.

William Chen, 26, makes $125 a day installing hardwood floors for a private contractor. He works five or six days a week during the spring and summer but had to take a job as a manager at McDonald’s to get through the winter. Chen, who lives in Malden with his girlfriend and a roommate, is trying to get a plumbing apprenticeship and wants to go back to school for “whatever I can get a career out of and make decent money.” But he’s not overly optimistic . “If I think too far ahead, I get frustrated,” he said.