Fidelity Investments, whose market share has been eroded by the stampede out of actively managed portfolios, on Wednesday launched two funds that will seek to exploit investors' desire for passive index funds.

Fidelity's two event-driven funds will look to capitalize on moves such as a company being deleted from an index or added to it. These events typically trigger automatic selling and buying by funds designed to follow a particular index.

"With passive investing, you're forced to copy corporate action. And when capital is forced to do something, that creates a special situation that can be exploited by investors," Fidelity executive Arvind Navaratnam said. He will serve as portfolio manager of Fidelity's Event Driven Opportunities Fund and the Advisor Event Driven Opportunities Fund.

Navaratnam said Facebook Inc's inclusion in the S&P 500 Index on December 20 is just one example of how big money in index funds will be forced to buy a particular company's stock. Analysts already have said Facebook's inclusion in the index will expand the company's investor base and likely bid up the price of the stock.

Conversely, opportunities also can arise from stocks that are deleted from an index. En masse selling by passively managed funds can beat down a company's share price, creating a potential opportunity for a bargain.

The Fidelity event-driven funds also will look to uncover mispriced stocks caused by special situations such as spin-offs, mergers and acquisitions, reorganizations and proxy fights, said Joseph DeSantis, chief investment officer of Fidelity's equity group.

DeSantis said these opportunities can have a lower correlation to the broader stock market over time, allowing investors in the event-driven funds to have more diversification in their portfolios. The event-driven funds will use the Russell 3000 Index as their benchmark.

Of course, passive investing is stronger than ever, reflected in the amount of money that has flowed into index and exchange-traded funds during the first 11 months of 2013.

Mutual funds and ETFs have seen inflows of $121.1 billion during the first 11 months of the year. But more than 100 percent of the net inflows are from passive funds, as active funds have had outflows of $10 billion, according to research firm Morningstar Inc.

Vanguard Group, which is known for its index funds, has dominated fund flows for several years running, with its funds attracting $65.3 billion in flows so far in 2013. Fidelity, best known for actively managed funds such as Magellan and Contrafund lagged far behind with year-to-date flows of $4.9 billion, according to Morningstar.