ORLANDO, Florida, June 3 : The Vanguard S&P 500 ETF, the index investing pioneer's flagship exchange-traded product, became the first in the history of ETFs to reach and exceed $1 trillion in assets, the investment firm confirmed on Wednesday.The Vanguard fund hit this milestone, the latest record in the remarkable ascent of exchange-traded funds, on Tuesday, less than 18 months after overtaking State Street Investment Management's SPDR S&P 500 ETF in assets, as investors looking for broad market exposure also sought out the lowest-cost funds. VOO levies a management fee of only 0.03 per cent, compared to 0.09 per cent for the State Street fund, which now is third in the three-way race between those two firms and BlackRock Inc..BlackRock, the world's largest asset manager, has the second-largest ETF tracking the Standard & Poor's 500 index, with its iShares Core S&P 500 ETF that now boasts $860 billion in assets and fees of 0.03 per cent, according to VettaFi. SPY, the market pioneer that helped open up the ETF market with its 1993 launch, now has $785 billion in assets."This is a key milestone," said Todd Rosenbluth, head of research at VettaFi. "Investors continue to turn to low-cost broad market exposure to gain access to the S&P 500 using VOO."