European debt investors are turning to U.S. corporate bonds as Mario Draghi’s quantitative easing program crushes borrowing costs in the euro-area.

Investors poured $347 million into the iShares $ Corporate Bond UCITS exchange-traded fund in the past week, making the fund the most popular among 327 fixed-income ETFs traded on European exchanges and tracked by Bloomberg. That’s up from $68 million the previous week and compares with about $131 million invested in the largest ETF for European company bonds.

ECB President Draghi’s commitment to an historic 1.1 trillion-euro ($1.2 trillion) asset purchase program has cut average borrowing costs for the region’s investment-grade companies to 1 percent as investors are squeezed out of safer markets like government debt. The average yield on similar U.S. bonds is 2.9 percent, Bank of America Merrill Lynch index data show.

“The ECB will have the effect of crowding investors out of markets where yields are already low and there is an inadequate supply of assets,” said Evan Moskovit, the New York-based lead money manager for global investment-grade credit at ING Investment Management International. “European investors are being pushed towards the U.S. in search of yield and because the market there is larger and more liquid.”

The iShares ETF buys investment-grade corporate debt issued by firms including Bank of America Corp, Verizon Communications Inc. and Ford Motor Co. The fund has attracted $435.8 million this year, Bloomberg data show.