Earlier this week, we wrote about the latest Ipsos poll of the Kentucky Senate race, and highlighted some reservations made by Jonathan Singer on inconsistencies between Ipsos’ turnout model and turnout statistics from the Kentucky Board of Elections. Clifford Young of Ipsos reached out to us via email in order to explain the math, and I thought it would only be fair to share his explanation with you:
[T]here was mention that our turnout estimates were incongruent with past Kentucky board of election turn out figures-that they were too high. On your specific point, we agree that the official Kentucky electoral turnout results are lower than our estimates (approximately 50% versus 70%).
We, however, shy away from using electoral board results as such data sources are notorious for double counting people that have moved and not culling those who have died. In our estimate, such data sources over-estimate by 20 to 30% the actual registered vote count.
Instead, we rely on the Census Bureau’s CPS (Current Population Survey) for our estimates. In November of every electoral year, the CPS includes a registered voter and turnout module on the survey and produces official estimates of turnout. See here for an example.
For full disclosure, in the below table, I include our estimates of registered voter turnout based on CPS data.
Percent Turnout in Kentucky by Registered Voters and Citizen Adult Population
Source: Current Population Survey, US Census
1998
2002
2006
Percent Registered
Voters who Voted
68%
68%
67%
Percent Total Population
of Citizens who Voted
46%
45%
49%
I think it worthwhile to point out that the Kentucky election results that you cite indicate that in 2006 there were a total of 2,766,288 registered voters, while the CPS estimates that there were 2,240,000 registered voters-an approximate 500,000 voter difference. If the Kentucky registered voter numbers were right, that would mean that about 91% of the adult citizen population is registered to vote–which is too high by any standard.
For these very reasons, we use the CPS estimates-with all the caveats in using sample surveys-as our turnout estimates.
Hope this clarifies our rationale. I hope this was not too esoteric. Keep up the good work.
Best,
Cliff Young
Managing Director, Public Sector
Ipsos Public Affairs
it makes sense.