In an attempt to generate move attractive payouts in a low-yield environment, investors have been dipping into lower-rated debt securities – high-yield U.S. bond sales have topped $12 billion this week, the highest weekly level in seven months.

Looking ahead, bond watchers anticipate the European Central Bank’s expanded bond purchasing program will continue to lift U.S. company bond prices and depress yields further.

Related: ECB Buying Spree Helps Lift U.S. Corporate Bond ETFs

“There is a feeding frenzy in the primary market for high yield and investment grade [debt],” Jim Sarni, managing principal at Payden & Rygel, told the Financial Times. “The [ECB’s corporate bond buying] is exacerbating the feeding frenzy. You have a mega investor in the game now … It means more crowding out. Central banks are systematically crowding out investors.”

For more information on the fixed-income market, visit our bond ETFs category.

iShares iBoxx $ High Yield Corporate Bond ETF