Q:

Stats on how attempts to circumvent Stack Overflow question blocks impact other sites

I would like to better understand how attempts to circumvent Stack Overflow question blocks impact other sites. I believe this can be estimated by finding out how many migrations to Stack Overflow were rejected because asker is question blocked.
Can we get some statistics on that please? I am particularly interested in numbers for last month, 2, 3 and 4 months, preferably broken down by "source" sites.

Not directly related, but while we're at it, I would appreciate to additionally see similar statistics of migrations to Stack Overflow that were rejected because of cross-posting.

A:

Ok, here are the numbers for the past 120 days of migrations. Extracting the intended destination site from the logs is enough of a pain that I didn't bother, but this is broken down by would-be source site:
Migrations blocked by q-bans Source Site Name 
---------------------------- --------- 
17                           Super User
4                            Server Fault
4                            Game Developers
10                           Statistical Analysis
1                            Web Apps  
11                           Webmasters
2                            Apple     
1                            Ubuntu    
10                           Unix and Linux
3                            WordPress 
63                           Programmers
4                            IT Security
3                            Graphic Design
7                            Database Administrators
2                            Code Review
1                            Code Golf 
1                            Signal Processing
1                            Academia  
1                            Computer Science
1                            Windows Phone
1                            ExpressionEngine
1                            Magento   
1                            Network Engineering Stack Exchange
1                            MathOverflow

Migrations blocked as dups Source Site Name 
-------------------------- --------- 
16                         Stack Overflow
7                          Super User
20                         Server Fault
2                          Mathematics
5                          Unix and Linux
10                         Programmers
1                          IT Security
6                          Database Administrators
3                          Mathematica
9                          MathOverflow

And finally, here's a fairly useless graph of q-ban-rejected-migrations-by-month for Progse, over the past 12 months:

All that said, this is a really imprecise way of gauging how many folks are asking questions on Progse because they got q-banned on SO. Here are some better numbers:

3884 users with accounts on Stack Overflow asked questions on Programmers during the past 120 days 
442 of those users have been q-banned on SO at some point in time 
320 of those users have been q-banned on SO during the past 120 days

Those 442 users asked 613 questions on Progse during this time period, and out of those questions:

424 were closed
429 were deleted
414 scored less than 0
76 scored more than 0

For comparison, 5038 questions were asked on Progse during the past 120 days by folks who didn't have q-banned accounts on SO, and out of those:

2724 were closed
2429 were deleted
2035 scored less than 0
1448 scored more than 0

Here's a slightly less useless graph to go with all that:

Tim's been working on a design for enhancing our our recidivism system to discourage this and other sorts of unproductive behavior.

