You can get a mordantly amusing sense of how reliable law school employment data has been by looking at the wildly divergent unemployment rates reported by otherwise very similar schools, and by examining what happens to those rates when US News changes its ranking methodology.
As regards the first issue, here are the percentages of the previous graduating class reported as unemployed-seeking work as of February 15, 2010 at four law schools:
Ave Maria: 33.7%
Florida International: 0%
What could possibly explain that more than one third of the class at an unranked fairly new Florida law school with an essentially open admissions policy was completely unemployed and seeking work nine months after graduation, while another unranked fairly new Florida law school with an essentially open admissions policy purportedly did not have a single member of its graduating class in this same situation? Why was the involuntary unemployment rate purportedly 90% lower at one horrible NYC area law school than at another such school?
Many similar pairings can be found by anyone with an inclination to browse through LST spreadsheets.
Here's an even more striking illustration of how phony much of the reported "employment" data from law schools has been: For many years, US News excluded graduates who were reported by their schools to be unemployed but not seeking work from the denominator when calculating graduate employment rates.
After ceasing this practice for a year because of a change in ABA reporting practices, the magazine stated in 2008 that it was going back to doing so, but included a stern warning to schools not to exploit this category in order to "spin" (trans: fraudulently mis-state) their employment rates). Subsequently, the majority of schools seemed to more or less heed this warning, as the median percentage of graduates reported to be unemployed not-seeking hovered around 2%, and the mode was zero percent. (For example in regard to the statistics above, in February of 2010 Touro reported having no graduates in the unemployed not-seeking work category, and Ave Maria reported just 2.3% of its graduates in this situation, even though a third of the classes at both schools didn't have jobs).
But some schools, it appears, ignored the warning, and jammed large numbers of their unemployed graduates into the "not seeking" category. Indeed, in February 2010 35 ABA schools reported having more than twice as many unemployed not-seeking graduates as unemployed-seeking graduates. (The Oscar in this category can be awarded to Santa Clara, which in 2010 and 2011 reported that 102[!] of its graduates were unemployed but not seeking jobs nine months after graduation, as compared to 29 unemployed graduates who were looking to acquire employment of some sort).
Then an awful thing happened: in March of 2011, just after schools submitted their numbers to NALP and US News, US News announced that henceforth it would treat unemployed not-seeking graduates as simply unemployed for the purposes of calculating nine-month employment rates. Miraculously enough, in February of 2012 the number of schools that reported having more than twice as many unemployed not-seeking graduates as unemployed-seeking fell from 35 to 4.