WisdomTree (NasdaqGS: WETF), the fifth-largest U.S. sponsor of exchange traded funds, said the WisdomTree MidCap Dividend Fund (NYSEArca: DON) topped $1 billion in assets under management.

DON debuted in June 2006. Its annual expense ratio is 0.38% and, like the other U.S.-focused WisdomTree dividend ETFs, pays a monthly dividend.

“There are a variety of dividend-focused funds and investment strategies, but we believe the WisdomTree MidCap Dividend Fund provides the broadest exposure to the mid-cap segment of the U.S. dividend-paying market. For investors looking for potential dividend income in a portfolio, we believe DON could serve as a core exposure to the U.S. mid-cap asset class,” said WisdomTree Chief Investment Strategist Luciano Siracusano in a statement.

DON tracks the WisdomTree MidCap Dividend Index, which “is dividend weighted annually to reflect the proportionate share of the aggregate cash dividends each component company is projected to pay in the coming year, based on the most recently declared dividend per share,” according to WisdomTree.

The index has a dividend yield of almost 3.1% with a price-to-book ratio of 2.4, according to issuer data. Nearly half of the almost 400 stocks held by DON have dividend yields in excess of the 10-year Treasury yield, currently 2.62%. [Dividends Gain an Advantage]

Over the past five years, DON’s underlying index has outperformed the S&P MidCap 400 Index by nearly 300 basis points and the Russell MidCap Value Index by 140 basis points, according to WisdomTree data. [Don’t Forget Mid-Caps]