你怎么会信chatGPT的一本正经胡说八道，而不信网友。帐户上都说了是institutional SP index，见内

看这两个links

https://institutional.vanguard.com/investments/product-details/fund/2040 这是机构买的SP500 index，费用比Vfiax低

https://investor.vanguard.com/investment-products/mutual-funds/profile/vgxrx#