The high and low ends of the M&A legal services market are becoming ever more stratified as billing rates for deal work dwarf other practices, according to a new survey by legal billing processing and analytics company LexisNexis CounselLink.

Lawyers who already command the highest rates clocked the fastest growth in billing rates last year, according to CounselLink’s examination of roughly $21 billion in invoices related to more than 1 million matters since 2009. The fees were paid by a wide variety of companies in different sectors. A quarter of the companies had annual revenues over $10 billion. Forty percent gross $1 billion to $10 billion annually, and the rest took in less than $1 billion a year.