SPDR S&P 500 (NYSEArca: SPY), the largest ETF by assets, gathered inflows of $6.1 billion in the latest week as the fund saw the heaviest buying in over three years.

Also, options volume on the fund spiked late Friday on rumors of central bank support for global financial markets.

For the week ended June 13, ETFs pulled in a net $9.1 billion with two-thirds of the inflows directed at SPY, according to Reuters. The S&P 500 fund, which holds $100.8 billion, experienced its heaviest inflows since October 2008.

The big inflows may not be a reliable bullish indicator because many large investors use SPY to trade and park cash on a short-term basis.

“ETFs are anecdotally believed to represent the investment behavior of institutional investors while mutual funds are thought to represent the retail investor,” Reuters reported.

Options contracts on SPY, the S&P 500 ETF, saw frenzied activity Thursday afternoon following reports citing G-20 sources that central banks were preparing coordinated action to provide liquidity to global markets.

Showing Page 1 of 2