PwC said mega deals, while increasing in number, continue to represent a relatively small proportion of total deal mix from a historic standpoint. Deals greater than $10 billion were up 66%, to $97 billion, for the first five months this year, versus $59 billion in the prior year. There were, however, only four such transactions in each period. PwC noted that the 2011 value of deals was heavily weighted by the $40 billion AT&T/T-Mobile announcement, and the $26 billion Duke Energy/Progress Energy announcement.

Middle-market activity (deals under $1 billion) continued to be a significant part of total activity, accounting for 94% of deal volume and 27% of deal value.

he growing inventory of portfolio companies ready to be sold out of funds nearing the end of their fund life, PwC said, led to private equity sales increasing significantly -- to 22 deals worth $23.9 billion this year. Last year, the 13 deals in that category were worth $3 billion.