<prompt> Human: Shouldnt they closely mirror each other? Why not just but VTI if thats going to be the case.  <response>: ETFs VTI are live, so you see the price fluctuate as intra-day trading occurs. Mutual funds VTSAX only settle trades at the end of the day, and their price may be delayed by a few hours after market close. The VTSAX up 0.04 is still Fridays amount. Todays hasnt been adjusted on most trackers yet. 