According to data from S&P Dow Jones Indices, preliminary results show that S&P 500 stock buybacks, or share repurchases, increased 18.1% to $118.1 billion during the second quarter of 2013, up from the $100 billion spent on share repurchases during the first quarter of 2013. Third-quarter data is not yet available.

Even without the third-quarter numbers, one thing is clear: Buyback ETFs are working this year. The PowerShares BuyBack Achievers Portfolio (NYSEArca: PKW) had a year-to-date gain of 31% at the end of the third quarter, making it the sixth-best market-based ETF this year, according to Dorsey Wright data.

The ETF has raked in over $1.3 billion in new assets this year, making it the second-best PowerShares ETF by that metric. Not only that, but PKW has a penchant for outpacing many of its underlying components and some of the largest share repurchasers that are not found in the NASDAQ Buyback Achievers Index. [Buyback ETF Topping Broader Market]

Howard Silverblatt, Senior Index Analyst at S&P Dow Jones Indices, noted a good chunk of the buyback activity is from Apple (NasdaqGM: AAPL), which spent $16 billion on share buybacks in the second quarter. But nonetheless, S&P Dow Jones Indices data show that for the 12-month period ending June 2013, S&P 500 companies increased their buyback expenditures by 4.7%, to $420.9 billion from the $402.0 billion posted in the prior 12-month period, according to a research note from S&P Capital IQ.