I collected the data from ABA for 2013, 2014, 2015, and 2016. I summed it all and calculated BigLaw or Federal Clerkship / Total Class Size. This by no means is the only measure to use. But I found it interesting.
It seems the top five are Columbia, Stanford, Harvard, Chicago, and Penn. Then there is a notable drop.
The remaining schools within the T13, except for Michigan and Berkeley, are about even.