(Reuters) - Vanguard Group's Standard & Poor's 500 ETF overtook rival State Street Global Advisors' SPDR S&P 500 Trust, on Tuesday to become the world's largest exchange-traded fund, according to data from FactSet.

The widely anticipated event was the result of $2.8 billion in outflows from SPY on Tuesday, in tandem with inflows of $305 million into the rival Vanguard fund the same day. That left VOO in the lead with assets of $632.2 billion by the end of the day on Tuesday, compared to $630.4 billion for SPY, the FactSet data showed.

The State Street ETF, launched in 1993, will retain the title of the oldest exchange-traded fund in the United States.

A third fund offering investors exposure to the Standard & Poor's 500 index, BlackRock's ( BLK ) iShares Core S&P 500 ETF, is challenging the market leaders, FactSet data shows. Its assets stood at $609.1 billion as of Tuesday.