What is the active share of a mutual fund

Suppose a fund’s benchmark has just four stocks: A at 40%, B at 30%, C at 20% and D at 10%. The fund holds A at 25%, B at 30%, doesn’t have expoure to C and holds D at 20%, and a non-index stock E at 25%. The differences are: 15 percentage points on A, zero on B, 20 on C (which the fund skipped entirely), 10 on D, and 25 on E. These add up to 70. Divide by two, and the active share is 35%—meaning 35% of the fund’s portfolio is invested differently from the index.