|Vote-Share Equations: November 2018 Update|
Presidential and Congressional
Vote-Share Equations: November 2018 Update, discusses the
November 2018 update of the vote-share equations. Forecasts for
2020 are also made.
This discussion assumes that the paper,
Presidential and Congressional
Vote-Share Equations, American Journal of Political Science,
January 2009, 55-72, has been read.
Compute your own prediction: The following link allows you to
compute your own predictions of the
2020 presidential and House elections.
Predictions: The current predictions of VP and VC for the 2020 election using the economic forecasts from the US model are:
G P Z VP VC November 14, 2018 1.2 2.4 1 45.7 53.0 February 28, 2019 1.2 2.2 1 45.6 52.9 April 26, 2019 1.2 2.0 1 45.4 52.8VP is the Democratic share of the two-party presidential vote, and VC is the Democratic share of the two-party vote in the House. Click the above "Compute your own predictions for 2020" for the definitions of G, P, and Z.
April 26, 2019, comment: The economic forecasts of G, P, and Z from the US model are little changed from the previous two forecasts, so the predictions of VP and VC are little changed. See the comment dated November 14, 2018, below for more details.
February 28, 2019, comment: The economic forecasts of G, P, and Z from the US model are little changed from the November 14, 2018, forecast, so the predictions of VP and VC are little changed. See the comment below for more details.
November 14, 2018, comment: The economic forecasts from the US model dated October 27, 2018 are used for this prediction. The US model is forecasting modest growth for the rest of the Trump administration. The per capita growth rate (at an annual rate) in the first three quarters of 2020 (G) is forecast to be 1.20 percent. The inflation rate at an annual rate in the first 15 quarters of the Trump administration (P) is forecast to be 2.40 percent. The number of strong growth quarters is forecast to be only 1, which was the second quarter of 2018. This economic forecast is thus neither boom nor bust. Conditional on these forecasts, the prediction for VP is 45.7 and the prediction for VC is 53.0. In this situation the Democrats are predicted to lose the presidential election by 4.3 percent points, larger than one standard error, and win the two-party House vote by 3.0 percent points, a little over one standard error. See the discussion of Table 6 on page 12 in the first paper linked above for alternative predictions, one with a booming economy and one with a recession.
Why is the presidential equation so pessimistic for the Democrats? The current case is the best possible one for the Republicans according to the equation: President running again and no negative duration effect. In this case it takes a weak economy to have the voting equation predict the Democrats getting close to 50 percent of the two-party vote. This analysis, of course, does not take into account the personalities of the candidates.
Data for downloading:
Previous update papers:
Web site material for previous elections: