I used a relatively simple model to generate the graph shown in the accompanying article. I ran weighted least-squares regressions against the logarithm of the number of days since the Inauguration and the usual array of dummy variables to account for differences in polling methods and “house effects.” Here are the results:
The use of the base-10 logarithm shows that Trump’s approval is estimated to have fallen by a bit over five percent between day ten of his term (log(10)=1) and day one hundred (log(100)=2). I use the percent approval rating in this regression to make the dummy variable coefficients more meaningful. A regression using the logit of the approval rating shows identical results.
These results show that polls conducted over the Internet or limited to registered voters tend to report a job approval figure about 1.5 percent higher than the consensus. The “house effects” variables indicate that polls conducted by YouGov/Economist average just under one percentage point less favorable toward Trump than the consensus. Job approval ratings from polls taken by SurveyMonkey, Politico/Morning Consult, and Rasmussen run from two to five percent higher than the consensus. Gallup, the most frequent pollster, does not deviate from the consensus.