The Vanguard Total Stock Market Index Fund Institutional Plus Shares (VSMPX) is one of the largest pooled equity vehicles in the world, but most readers searching for it cannot actually buy it. VSMPX is a mutual fund share class, not an ETF, and Vanguard reserves it for institutional clients writing checks measured in hundreds of ... VSMPX Tracks VTI Perfectly at Half the Cost, but There’s a Catch for Individual Investors