It looks like they were contracted for 175 shows per year starting in 1998, which is the same year they went to a four-day tape week so Barker would only have to do one show per day on Tue, Wed and Thu. They lost 10 shows in 1999 due to Bob's surgery and 10 shows in 2000 due to that "weird circumstance".
Starting with the season beginning September 2001 they've taped a consistent 175 shows per year until 2007 when Drew arrived and it went up to 190 (38 weeks). Maybe they were contracted for 39 weeks but lost a week due to Drew getting his arm stuck in the turntable?
From 1993 to 1997 it looks like they were doing 185 shows per year.
Here is your chart with years added, based on an early September start:
1972 Season 1: 254 – 254
1973 Season 2: 229 – 483
1974 Season 3: 253 – 736
1975 Season 4: 214 – 950
1976 Season 5: 213 – 1,163
1977 Season 6: 228 – 1,391
1978 Season 7: 209 – 1,600
1979 Season 8: 191 – 1,791
1980 Season 9: 205 – 1,996
1981 Season 10: 196 – 2,192
1982 Season 11: 208 – 2,400
1983 Season 12: 197 – 2,597
1984 Season 13: 195 – 2,792
1985 Season 14: 186 – 2,978
1986 Season 15: 191 – 3,169
1987 Season 16: 186 – 3,355
1988 Season 17: 184 – 3,539
1989 Season 18: 177 – 3,716
1990 Season 19: 186 – 3,902
1991 Season 20: 178 – 4,080
1992 Season 21: 177 – 4,257
1993 Season 22: 185 – 4,442
1994 Season 23: 183 – 4,625
1995 Season 24: 183 – 4,808
1996 Season 25: 185 – 4,993
1997 Season 26: 184 – 5,177
1998 Season 27: 175 – 5,352
1999 Season 28: 165 – 5,517
2000 Season 29: 164 – 5,681
2001 Season 30: 175 – 5,856
2002 Season 31: 175 – 6,031
2003 Season 32: 175 – 6,206
2004 Season 33: 175 – 6,381
2005 Season 34: 175 – 6,556
2006 Season 35: 175 – 6,731
2007 Season 36: 190 – 6,921