Also, what percentage of index fund investors hold those shares only in the short term? I thought much of the point of index fund investing is that it's great

Also, what percentage of index fund investors hold those shares only in the short term? I thought much of the point of index fund investing is that it's great for a relatively low-effort, reasonably-diversified buy-and-hold strategy on the part of anyone from individual investors planning for retirement to institutional investors managing pensions?