plunkers vs plunk nots

So far this year, the top 10 teams in hit batters have a combined ERA of 4.75 while the bottom 10 have a combined 4.01 ERA. This is the biggest difference in earned run average between the top and bottom third of teams in plunks since 1937. In 1990, the top third of teams in hit batters posted a better ERA than the bottom third by 2 hundredths of a run, so it is possible for teams that hit a lot of batters to still be effective pitching staffs, but even that year the middle third was better. The ERA of the top third in plunks hasn't been below both other thirds since 1967.
Here are the combined ERAs for the top, middle, and bottom third of teams in the majors for each year back to 1980:

Year	Top Third	Middle Third	Bottom Third	Total MLB ERA
2005	4.75	4.10	4.01	4.30
2004	4.52	4.69	4.18	4.46
2003	4.33	4.79	4.08	4.40
2002	4.64	4.27	3.92	4.28
2001	4.56	4.50	4.20	4.42
2000	4.92	4.61	4.78	4.77
1999	5.06	4.65	4.41	4.71
1998	4.57	4.38	4.35	4.43
1997	4.63	4.24	4.27	4.39
1996	4.90	4.55	4.37	4.61
1995	4.53	4.56	4.29	4.45
1994	4.56	4.71	4.30	4.51
1993	4.24	4.35	4.02	4.19
1992	3.76	3.80	3.68	3.75
1991	4.05	3.86	3.82	3.91
1990	3.88	3.80	3.90	3.86
1989	4.09	3.46	3.55	3.71
1988	4.13	3.62	3.44	3.73
1987	4.47	4.20	4.20	4.29
1986	4.23	3.78	3.88	3.97
1985	4.29	3.71	3.66	3.89
1984	4.07	3.83	3.54	3.81
1983	4.07	3.91	3.64	3.87
1982	3.90	3.83	3.85	3.86
1981	3.61	3.74	3.41	3.58
1980	4.06	3.79	3.67	3.84