~20% of S&P 500 companies have reduced their share count by at least 4% yoy in each of the last five quarters, and that appears to be continuing into Q2:
But not completed one 
However, it means earnings per share is 4% higher and P/E is 4% lower than a year ago for those companies, which helped stocks outperform.
The question might be the price 
One thing certain: There is simply less “stock” in the stock market.
As of the end of 2014, outstanding share count was well below where it was about 10 years ago, and the lowest in FactSet’s data set.
While net flows into US stocks have been relatively flat since 2006, net issuance has plummeted.
The biggest factor behind the decline in IPOs is the heightened volatility in the stock market. 
Secondary offerings is also dropping.
Listed firms is disappearing
The number of firms with shares publicly listed in the University of Chicago’s Center for Research in Security Prices aggregate index has fallen to 3,267 from a peak of 6,364 in 1997. Reason:
“Between the lack of IPO activity, the pick-up of M&A, and buybacks, the US equity world is becoming smaller and smaller, and this could be one of many reasons why active managers are lagging behind their indexes. 
Companies may not want to come public due to the additional cost of Sarbanes-Oxley or the fact that the private market has become a bigger source of financing than it has been in the past.”
In 2015, announced buybacks are up 50% compared to 2014.
however, that the increase in announced buybacks is not bringing about an increase in completed buybacks and also notes that much of the increase in buyback announcements comes from a few big players.
For example, Apple and General Electric have both announced $50 billion buybacks this year, while the Home Depot said it would be repurchasing $18 billion worth of shares. And Gilead Sciences, Qualcomm, Pepsi, American Express, and Merck also have all announced buybacks worth $10 billion or more.[
Buying back stock is, for example, Warren Buffett’s preferred way of returning cash to shareholders (rather than paying a dividend). But Buffett thinks share buybacks make sense when stocks are undervalued.
“IPOs are a higher-risk proposition because the market isn’t totally sure of their value. So you want a relaxed market when you enter with that higher risk.”
“January and February are typically bad months for IPOs anyway,” “Typically, these companies have financial periods ending in March so they wait for that next set of statements before going to market.”
The argument is that with fewer companies to choose from, active managers are forced to crowd into certain stocks. Crowding makes it impossible to differentiate returns and causes these managers