Why? The most significant explanation is also the simplest — free money.

In 2006, Congress extended the federal Direct PLUS Loan program to allow a graduate or professional student to borrow the full amount of tuition, no matter how high, and living expenses. The idea was to give more people access to higher education and thus, in theory, higher lifetime earnings. But broader access doesn’t mean much if degrees lead not to well-paying jobs but to heavy debt burdens. That is all too often the result with PLUS loans.

The consequences of this free flow of federal loans have been entirely predictable: Law schools jacked up tuition and accepted more students, even after the legal job market stalled and shrank in the wake of the recession. For years, law schools were able to obscure the poor market by refusing to publish meaningful employment information about their graduates. But in response to pressure from skeptical lawmakers and unhappy graduates, the schools began sharing the data — and it wasn’t a pretty picture. Forty-three percent of all 2013 law school graduates did not have long-term full-time legal jobs nine months after graduation, and the numbers are only getting worse. In 2012, the average law graduate’s debt was $140,000, 59 percent higher than eight years earlier.

This reality has contributed to the drastic drop in law school applications since 2011, which has in turn exacerbated the problem — to maintain enrollment numbers, law schools have had to lower their admissions standards and take even more unqualified students. These students then fail to pass the bar in alarmingly high numbers — in 2014, the average score on the common portion of the test was the lowest in more than 25 years.

How can this death spiral be stopped? For starters, the government must require accountability from the law schools that live off student loans. This year, the Obama administration extended the so-called gainful employment rule, which ties a school’s eligibility to receive federal student loans to its success in preparing graduates for jobs that will enable them to repay their debt. The rule currently applies only to for-profit law schools, all of which, given their track records, would fail to qualify for federal loans.