Years in Crosscheck: 2014-2015
Pennsylvania provided a breakdown of their Crosscheck results from 2014 which give some insight into data quality. Here is a breakdown of their 2014 stats:
Voter records sent to Crosscheck: 8,224,219
Crosscheck records returned: 371,923
Unique PA voters identified as "potential duplicate registrants"¹: 344,346
"Potential duplicate registrants" who did not match on last four digits of social security number: 151,556
¹The difference between total records returned and unique PA voters is due to the fact that some PA voters potentially matched with voters in more than one state.