Investors are using some of the largest and most highly traded ETFs to buy U.S. stocks, which were set for their fourth straight week of gains in afternoon trading Friday.

For example, over the first four days of the week, the top-selling ETFs were SPDR S&P 500 (NYSEArca: SPY) and the Nasdaq-100 PowerShares QQQ (NasdaqGM: QQQ) with inflows of $3.7 billion and $1.4 billion, respectively, according to IndexUniverse data.

Meanwhile, the small-cap iShares Russell 2000 (NYSEArca: IWM) raked in nearly $500 million between Monday and Thursday. [Investors Pumping $2 Billion a Day Into U.S. Stock ETFs]

The S&P 500 was on track of a weekly advance of 0.4% in afternoon dealings Friday while the Dow rose 0.3%. Both U.S. blue-chip stock indices hit new record highs this week amid second-quarter earnings season. However, the Nasdaq-100 QQQ ETF was set for a decline of 1.2%.

“As with every earnings season, you have some high profile misses, but still the market is obviously taking it in stride. We think it’s encouraging we’re shaking off the tech disappointments,” said Ryan Detrick, senior technical strategist at Schaeffer’s Investment Research, in a Reuters report.

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