"Mergers 101" prompted some reader response curious for more detail behind my concluding observation about how the composition of the AmLaw 200 as of 2004 differed from that as of 1999.  Here are the raw numbers:

• 11 firms were acquired
• 3 dissolved
• 8 fell out of the AmLaw 200
• 9 merged and survived as a different entity
• and there were 23 new entrants between 1999 and 2004 (totaling the "54" I cited).

Fleshing this out further, one can demonstrate that there was far more "turnover" among the AmLaw 101-200 than among the first 100 firms. 

• 23 firms on the list in 1999 did not reappear in the same form or at all in 2004
• Of these, 18 were AmLaw 101-200 firms
• Of the 5 AmLaw 100 firms that did not reappear, 2 dissolved, 2 were acquired by another AmLaw 100 firm, and one was acquired by a Global 100 (non-AmLaw) firm.

Also demonstrating more volatility in the ranks of the 101-200 firms is that all 23 new entrants as of 2004 stood in the 101-200 rankings.  The highest-ranked newcomer, at #108, is Kasowitz, Benson, Torres & Friedman, which does plaintiffs work. The second-highest newcomer, at #125, will be a surprise to few:  Boies-Schiller.

This would be an opportune moment for me to post an editorial/housekeeping note about data from the Law Firm Research Project:  Although Prof. William Henderson of Indiana University Law School/Bloomington and I have worked collaboratively and jointly to assemble and develop the raw data, "Adam Smith, Esq." is my responsibility and mine alone.  As they say up-front in books, "I humbly acknowledge the gracious and essential assistance of many of my betters, but any errors or omissions that follow are strictly my own."

Thanks to all who helped motivate this supplemental info!