UPDATED Mar. 13, 2023, at 3:53 PM

FiveThirtyEight’s Pollster Ratings

Based on the historical accuracy and methodology of each polling organization’s polls.

B/C

Iowa State University Center for Survey Statistics and Methodology

Polls analyzed	3
Races called correctly	67%
Most recent cycle	2016
Affiliated with AAPOR/Roper	No
Other names

What are pollster ratings?

How accurate are the polls from Iowa State University Center for Survey Statistics and Methodology?

Polls conducted within 21 days of an election (based on the poll’s median date) are used to determine the pollster’s grade.

2016

Key

A = Adults

RV = Registered voters

V = Voters

LV = Likely voters

Dates	Sample	Race	Methodology	Poll margin	Election margin	Difference
Jan 5-22	283LV	President (IA) Republican primary	Live Phone	Poll Cruz +6.9	Actual Cruz +3.3	Difference 3.6
Jan 5-22	356LV	President (IA) Democratic primary	Live Phone	Poll Clinton +2.4	Actual Clinton +0.3	Difference 2.1

2012

Dates	Sample	Race	Methodology	Poll margin	Election margin	Difference
Dec 8-18	333LV	President (IA) Republican primary	Live Phone	Poll Romney +12.6	Actual Santorum +0.0	Difference 12.6

How this works

FiveThirtyEight’s pollster ratings are calculated by analyzing the historical accuracy of each polling organization’s polls along with its methodology. Accuracy scores are adjusted for the type of election polled, the poll’s sample size, the performance of other polls surveying the same race and other factors. We also calculate measures of statistical bias in the polls. When a pollster publishes multiple versions of the same survey (for example, versions with and without third-party candidates included), FiveThirtyEight uses an average of the different versions to calculate the pollster’s rating. However, all versions of these polls are listed here. Read more about our methodology»

Download this data as an Excel spreadsheet or get it on GitHub.

Design and development by Elena Mejía and Aaron Bycoffe. Research by Mary Radcliffe, Cooper Burton and Dhrumil Mehta. Copy editing by Andrew Mangan. Visual editing by Christopher Groskopf. Statistical model by Nate Silver.

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