They list the attendance next to all their games throughout their history in the media guide.
I'm embarrassed for them. Regularly 15-20,000 empty seats for their big game against hated rival MU. Years when undefeated KU teams that were ranked took the field with thousands of empty seats at KU Memorial Stadium. Years when they came off nice seasons the year before and never even broke 40,000 for their opening home games. Bowl eligibility on the line and 20,000 empty seats. Multi-game conference winning streaks with decent teams and still thousands of empty seats. Decent to good KU teams playing decent to good non-conference games at home with thousands of empty seats. They had two home sell outs during their Orange Bowl season.
Here's a fun little list, particularly when they'll tell you that they hate MU so much more than K-State:
All @ KU Memorial Stadium
1971K-State 51,151
MU 43,464
1973K-State 51,574
MU 44,062
1975K-State 50,338
MU 46,851
1977 K-State 47,858
MU 43,148
1979K-State 48,627
MU 34,599
1981K-State 51,600
MU 47,500
1983K-State 49,300
MU 38,400
1985K-State 40,000
MU 22,000
Big 8 had a schedule adjustment, so they ended up playing @ K-State and @MU for two straight years
1988K-State 35,000
MU 25,000 (The Marcum/Fredrick AD Wheel of Attendance Truth was really hitting its stride about now, highlighted by nice round numbers)
1990K-State 45,000
MU 30,000
1992K-State 48,604
MU 30,845 (this was for a 3rd place in the Big 8 KU team. 21,00 empty seats, no wonder they lost, how deflating to come out of the tunnel for this game and have 21,000 empty seats, pathetic)
1993MU 31,500
1994K-State 48,800
1995MU 46,300 KU went into the game ranked
11th.
1996K-State 48,800 Largest KU home crowd of the year, zero sell outs coming off a 10-2 season.
1997MU 38,000
From here I'll just do MU, because K-State had been and would continue to bring 1000's of fans.
Attendance for the remainder of the MU games played in Lawrence
38,000
42,300
38,500
50,071
48,238