Number of users with activity on the main site in the last year: 4221312
Number of users who have posted non-deleted questions or answers on Meta in the last year: 3256
Number of users who have posted non-deleted comments on Meta in the last year: 4959

If you do this without limiting to activity in the last year, you will get 10779915 for the total number of non-deleted users (ever) and 19001 for the number of non-deleted users with non-deleted Meta posts (ever), giving...

Number of votes in the last year: 1408932 (ignoring votes by the community user)
Number of votes by Meta Users in the last year: 68409 (ignores downvotes on now-deleted posts, I think)
Percentage: 4.86%

Number of suggested edit votes in the last year: 906061
Number of suggested edit votes by Meta Users in the last year: 208118
Percentage: 23.0%

Number of non-deleted answers posted in the last year: 2440700
Number of non-deleted answers posted by Meta Users in the last year: 305767
Percentage: 12.5%

Number of post history changes in the last year: 12675953
Number of post history changes in the last year by Meta Users: 1369123
Percentage: 10.8%

Number of non-deleted comments in the last year: 7641649
Number of non-deleted comments by Meta Users in the last year: 1245870
Percentage: 16.3%

Number of users with activity on the main site in the last year: 4,221,312
Number of users who have posted non-deleted questions or answers on Meta in the last year: 3,256
Number of users who have posted non-deleted comments on Meta in the last year: 4,959

If you do this without limiting to activity in the last year, you will get 10,779,915 for the total number of non-deleted users (ever) and 19,001 for the number of non-deleted users with non-deleted Meta posts (ever), giving...

Number of votes in the last year: 1,408,932 (ignoring votes by the community user)
Number of votes by Meta Users in the last year: 68,409 (ignores downvotes on now-deleted posts, I think)
Percentage: 4.86%

Number of suggested edit votes in the last year: 906,061
Number of suggested edit votes by Meta Users in the last year: 208,118
Percentage: 23.0%

Number of non-deleted answers posted in the last year: 2,440,700
Number of non-deleted answers posted by Meta Users in the last year: 305,767
Percentage: 12.5%

Number of post history changes in the last year: 12,675,953
Number of post history changes in the last year by Meta Users: 1,369,123
Percentage: 10.8%

Number of non-deleted comments in the last year: 7,641,649
Number of non-deleted comments by Meta Users in the last year: 1,245,870
Percentage: 16.3%

Number of users with activity on the main site in the last year: 489981
Number of users who have posted non-deleted questions or answers on Meta in the last year: 3256
Number of users who have posted non-deleted comments on Meta in the last year: 4959

Percentage, based on Meta commenters, within last year: 1.01%

Percentage, based on Meta posters, within last year: 0.665%

If you do this without limiting to activity in the last year, you will get 1360931 for the total number of users (ever) and 18973 for the number of users with Meta posts (ever), giving...

Percentage, based on Meta posters, ever: 1.39%

Those are higher than 0.015%, and aren't even accounting for whether the users are "active". So unless the 0.015% figure is really supposed to include people who don't have accounts, it's probably wrong. (Remember I'm not a data scientist.)

Number of users with activity on the main site in the last year: 4221312
Number of users who have posted non-deleted questions or answers on Meta in the last year: 3256
Number of users who have posted non-deleted comments on Meta in the last year: 4959

Percentage, based on Meta commenters, within last year: 0.117%

Percentage, based on Meta posters, within last year: 0.0771%

If you do this without limiting to activity in the last year, you will get 10779915 for the total number of non-deleted users (ever) and 19001 for the number of non-deleted users with non-deleted Meta posts (ever), giving...

Percentage, based on Meta posters, ever: 0.176%

Those numbers are higher than 0.015%, and aren't even accounting for whether the users are "active". So unless the 0.015% figure is really supposed to include people who don't have accounts, it's probably wrong. (Remember I'm not a data scientist.)

These numbers are a lot closer than they were in the previous version of this post. But that only makes these other statistics more impressive...

This made me curious so I started messing with SEDE.

To keep things simple, I'm going to look at the last year. Of course, since I'm just using SEDE, this will not take into account the hordes of Google lurkers.

That's higher than 0.015%, and it isn't even accounting for whether the users are "active". So unless the 0.015% figure is really supposed to include people who don't have accounts, it's probably wrong. (Remember I'm not a data scientist.)

Bonus question: What fraction of free labour on Stack Overflow (writing answers/reviewing/helping others with edits&comments etc.) is carried out by these .015%?

This made me curious so I started messing with SEDE. To keep things simple, I'm going to look at the last year. Of course, since I'm just using SEDE, this will not take into account the hordes of Google lurkers.

Those are higher than 0.015%, and aren't even accounting for whether the users are "active". So unless the 0.015% figure is really supposed to include people who don't have accounts, it's probably wrong. (Remember I'm not a data scientist.)

Bonus question: What fraction of free labour on Stack Overflow (writing answers/reviewing/helping others with edits&comments etc.) is carried out by these .015%?