The Brown Bear and Historical Data

In this post, the Brown Bear will describe how he uses data from the past four presidential elections to calculate each state's Degree of Partisanship and then combines this with the National Margin to determine a preliminary winner of the presidential race in each of the fifty states.

As an example we will consider the state of Iowa. First the Brown Bear determines the percentages received by the Democrat and the Republican for each of the past four presidential elections. In 1988, Bush defeated Dukakis 53.92% to 46.08%. 1992, Clinton defeated Bush 43.28% to 37.69%. In 1996, Clinton defeated Dole 49.94% to 41.44%. In 2000, Gore had more votes (but lost in the electoral college) 48.88% to 48.36%. Then the Brown Bear determines the percentages received by the Republican and the Democrat in each state for each of the last four presidential elections. For Iowa those results are:

1988: D 55.19% -- R 44.81%; 1992: D 43.60% -- R 37.55%;

1996: D 50.84% -- R 40.54%; 2000: D 49.03% -- R 48.71%.

<> Then the Brown Bear subtracts the National result from the state result for each party for each state for each election. For Iowa these results are:

1988: D 55.19% - 46.08% = 9.11% R 44.81% - 53.92% = -9.11%

1992: D 43.60% - 43.28% = 0.32% R 37.55% - 37.69% = -0.14%
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1996: D 50.84% - 49.94% = 0.90% R 40.54% - 41.44% = -0.90%

2000: D 49.03% - 48.88% = 0.15% R 48.71% - 48.36% = 0.35%

The Brown Bear then multiplies these results by the following weights. For 1988, 2; for 1992, 3; for 1996, 6; for 2000, 12. For Iowa, these products are:

1988: D 9.11% x 2 = 18.22% R -9.11% x 2 = -18.22%

1992: D 0.32% x 3 = 0.96% R -0.14% x 3 = -0.42%

1996: D 0.90% x 6 = 5.40% R -0.90% x 6 = -5.40%

2000: D 0.15% x 12 = 1.80% R 0.35% x 12 = 4.20%

The Brown then adds these products for each party. For Iowa, these sums are:

D 18.22% + 0.96% + 5.40% + 1.80% = 26.38%

R -18.22% – 0.42% – 5.40% + 4.20% = -19.84%

The Brown Bear then divides these sums by the sum of the weights (2 + 3 + 6 + 12 = 23). For Iowa these results are: D 26.38% / 23 = 1.15% -- R -19.84% / 23 = -0.86%. The Brown Bear then subtracts the Republican Result from the Democratic result to obtain each state's Degree of Partisanship. Iowa's Degree of Partisanship is 1.15% - (-0.86%) = 2.01% (in favor of Democratic candidates).

To obtain a preliminary result for each state, the Brown Bear takes the National Margin (as calculated in The Brown Bear National Margin Parts One and Two) and adds it to each state's Degree of Partisanship (if the National Margin favors the Republican candidate, the Brown Bear makes the National Margin negative). Using the National Margin calculated in the previous posts in this series, the result for Iowa is 2.01% + (-3.55%) = -1.54%. Thus, the preliminary result for Iowa is a Republican victory, but with a margin so small, the Brown Bear would designate it Tossup (B).