For some reason, this article eluded me until now. Michael Simkovic and Frank McIntyre conducted a study assessing the long term value of a law degree. Their conclusion: the mean pre-tax lifetime value of a JD is a million dollars. Even at the 25th percentile, they calculate the value of a JD at $350,000 over a lifetime. They conclude the present value of a law degree is greater that its cost for most students.
This study doesn't view the JD in isolation, but rather attempts to study a law degree in comparison to the alternative paths a potential law student might pursue.
I haven't had time to review this study in depth, though I'm confident that readers will do so. It cannot and does not account for changes in the legal market going forward. These changes could radically alter the value proposition of a JD. And as Kyle McAfee has pointed out, this study in no way addresses questions of transparency. But an empirical contribution to these ongoing debates seems quite worthwhile.
H/T Inside Higher Ed
Update: Unfortunately, I have felt it necessary to unpublish certain comments to reduce the number of personal attacks. Sometimes it's hard to tell the difference between a fair (if generally unfriendly) request for a response from genuinely unsportsman-like conduct, but I've tried. Mea culpa if others don't share my judgment. I hope I speak for many readers when I say that I don't find this sort of debate either useful or uplifting.