Table 2.

The estimated values of the polarization utility u_p in each Congress. The 14 Congresses with the presidential election held in the preceding year increase u_p on average by 11.3% compared to the corresponding previous Congresses while the 15 Congresses with midterm elections (during which the President passes half of his term), decrease the polarization utility u_p by −1.5% on average. Moreover, in the first three decades, the average polarization utility grew slowly by 0.056, so 18.1% on average in Presidential election Congresses. All this growth was gained in four Presidential elections in which the newly elected President and his predecessor belonged to different parties; each of these elections contributed growth of 0.115 so 36.4%, on average. By contrast, the polarization utility decreased by −0.043 or −9.3% in midterm election Congresses, raising only 14.3% over 30 years. In the latest three decades, the polarization utility grew in both types of Congresses with similar average rates, of 0.023 or 4.6% for midterm election Congresses, and 0.21 or 7.3% for Presidential election Congresses. From the 100th Congress to 114th Congress the polarization grew 77.5%, so five times higher than in the earlier period. Notably, 6 of 14 Presidential election Congresses are associated with the polarization utility u_p > 0.5 while only one of 15 midterm election congresses had such high polarization utility.

midterm election congresses				presidential election congresses
number	up	change	percentage (%)	number	up	change	percentage (%)
86th	0.3	−0.05	−14.3	87th*	0.54	0.24	80.0
88th	0.4	−0.14	−25.9	89th	0.37	−0.03	−7.5
90th	0.32	−0.05	−13.5	91st	0.43	0.11	34.4
92nd	0.38	−0.05	−11.6	93rd	0.31	−0.07	−18.4
94th	0.33	0.02	6.5	95th	0.4	0.07	21.2
95th	0.4	0.00	0.00	97th	0.44	0.04	10.0
98th	0.43	−0.01	−2.3	99th	0.46	0.03	7.0
100th	0.4	−0.06	−13.0	101st	0.47	0.07	17.5
102nd	0.65	0.18	38.3	103rd*	0.61	−0.04	−6.2
104th	0.54	−0.07	−11.5	105th*	0.61	0.07	13.0
106th	0.5	−0.11	−18.0	107th*	0.5	0.00	0.0
108th	0.52	0.02	4.0	109th*	0.57	0.05	9.6
110th	0.48	−0.09	−15.8	111th	0.42	−0.06	−12.5
112th*	0.66	0.24	57.1	113th*	0.73	0.07	10.6
114th	0.71	−0.02	−2.74
86th–100th	0.370	−0.043	−9.3		0.421	0.056	18.1
101st–114th	0.580	0.021	7.3		0.559	0.023	4.6
All	0.468	−0.013	−1.5		0.481	0.039	11.3
	4 positive, 10 negative, 1a				9 positive, 4 negative, 6a

^aDenotes the polarization utility u_p over 0.5, marked by italic font in the u_p column.