After two pension funds filed suit against BlackRock’s iShares on its securities lending practices, exchange traded fund investors are getting a better glimpse into the way fund providers operate.

Securities lending is a practice where mutual funds and ETFs pay agents to lend out shares in their portfolios – the funds are created with exposure to an underlying basket of securities – to other traders and thereby earn interest, writes Ian Salisbury for the Wall Street Journal. [ETF Securities Lending in Focus on iShares Suit]

According to research firm Markit, the practice helps generate about $10 billion in annual revenue for mutual funds and other investment pools. [How ETF Securities Lending Works]

Recently, a lawsuit was filed, contending that BlackRock did not give enough of the extra revenue from securities lending back to shareholders. BlackRock maintains that it remits about two-thirds of its revenue from securities lending to investors while the rest helps cover costs and boost performance.

Experts, though, see the lawsuit as a catalyst for greater transparency into securities lending practices.

“You want sunlight,” William Birdthistle, a law professor at the Illinois Institute of Technology, said in the WSJ article. “Lawsuits like this can provide an investor education.”