In my county, we have identified infrequent voters by using the voter history portion of the voting rolls.  Here's how:  After feeding the text file of voter information obtained from the county registrar of voters into a set of spreadsheets, we first wrote two sets of "if-then-else" spreadsheet code.

The first set of code computed whether or not a voter was eligible to vote in an election by detecting whether or not a cell was blank.  A blank cell in the spreadsheet would indicate non-eligibility for that particular election and be assigned a value of zero.  All other cells has either a Y (yes), an N (no), or an A (absentee) and we were assigned a value of 1. All the ones were then summed up to obtain the number of elections in which each voter was eligible to vote.  The second set of code sorted out the Ys, As, and Ns and assigned a value of 1 for a Y or an A and assigned a value of 0 for an N or a blank.  These sets of ones were then summed up to compute the number of elections in which each voter actually voted.  Then the number of eligible elections was divided into the number of elections in which each voter actually voted and multiplied by 100.  The result was the percent of eligibile elections in which each and every voter in our county voted.

The entire voter file can then be sorted by the voting percentage in ascending order so that the low scores show up first and these voters can be contacted first.  Two minor glitches:  (1) a voter registered after the last election will have an "infinite" score (zero votes divided by zero eligible elections) and show up after the voters who vote in every election (100% score), (2) sometimes the voter history portion of the text file from the county registrar of voters has to be cleaned up, i.e. "Yes" entries converted to "Y", blank spaces removed, etc.  KEY OBSERVATION:  The number of Democrats who are infreqent voters is higher compared to the GOPigs.  Get-Out-The-Vote efforts matter a lot!   Hope this helps.