Vote-Share Equations: November 2018 Update
Background: The paper, 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.
Compute your own predictions for 2020

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     1.20   2.40     1     45.7   53.0 
VP 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.

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:
Data back to 1876. (The November 2018 Update used data back to 1916 only.) Data back to 1876
Quarterly data back to 1877:1 on nominal GDP, real GDP, population. Quarterly data back to 1877:1

Original paper:
1978---elections through 1976.

Previous update papers:
1982---elections through 1980.
1988---elections through 1984.
1990---elections through 1988.
1996---elections through 1992.
1998---elections through 1996.
2002---elections through 2000.
2006---elections through 2004.
2010---elections through 2008.
2014---elections through 2012.

Non technical discussions:
"Econometrics and Presidential Elections"
Predicting Presidential Elections and Other Things (Chapters 1, 3, and 4)

Web site material for previous elections:
Old site material for the 1996 election
Old site material for the 2000 election
Old site material for the 2004 election
Old site material for the 2008 and 2010 elections
Old site material for the 2012 and 2014 elections
Old site material for the 2016 and 2018 elections

Related work:
Interpreting the Predictive Uncertainty of Elections
The Ranking Assumption: Senate 2014
The Ranking Assumption: President, Senate, House 2016
The Ranking Assumption: Senate 2018