"No way this reflects real movement in public opinion -- too bumpy" [View all]

[bluewater]

says The Ecnomist's data journalist, G. Elliot Morris, about the RCP POLLS tracker.

Link to tweet

The RCP Poll tracker just graphs the simple, unweighted average of the last 5 polls or so, yielding that "bumpy" looking chart, as G. Elliot Morris colloquially described it, that over reacts to changes in a few recent polls.

The Economist's Poll tracker takes a more sophisticated approach:

Methodology
We estimate support for each candidate using a statistical method called Bayesian dynamic Dirichlet regression. The model aggregates polls over the course of the campaign, putting more weight on polls conducted recently, less on those with small sample sizes and accounting for “house effects”—the tendency for some polling firms to over- or underestimate support for certain candidates. We exclude polling firms that do not use rigorous methods. In the past, surveys conducted over the phone with a live interviewer or with online survey-takers that use well-thought-out methodologies have been more reliable than other methods.

Check out all the results at:

https://projects.economist.com/democratic-primaries-2020/