ETF investors are making a hugely bullish bet

Traders work on the floor of the New York Stock Exchange.
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While others were freaking out over the past week about the possibility of a U.S. debt default, exchange-traded funds focused on stocks were rolling in cash.

The ever-growing $1.6 trillion ETF space, which remains largely the province of short-term traders, raked in a gaudy $10.5 billion in the week ended Wednesday.

It was a testament both to Wall Street's blase attitude toward the prospects of an actual default as well as a bet that with the crisis out of the way—at least for now—the market's near-term direction is likely higher.