Functionally, a literal handful per season which are typically caught and prosecuted.
The right leaning Brookings and Heritage foundations dug into the numbers and found this
"Across the entire country, and utilizing a maximally inclusive estimate, between six and 46 cases of mail voting fraud were identified in each general election"
Table:
Year Total mail voting fraud percentage (out of total mail ballots cast)
2016 0.000089%
2018 0.000024%
2020 0.000051%
2022 0.000010%
Average 0.000043%
