I'd love to eventually look into how BTT attendance fluctuates with certain teams playing in certain locations, but I looked back through Wikipedia at the attendance for every Big Ten Tournament. First, I list the average by location (excluding the one game in 2020 and the reduced attendance in 2021). Then, there is a list by year for the average attendance.
AVERAGE BTT ATTENDANCE BY LOCATION
Chicago: 19,231
Indianapolis: 16,729
New York (MSG): 15,165 (1 year - 2018)
Washington, DC: 13,240 (1 year - 2017)
AVERAGE BTT ATTENDANCE BY YEAR
2001: 21,984
2005: 21,770
1998: 21,711
2013: 20,757
2000: 20,611
1999: 19,804
2002: 18,996
2007: 18,882
2003: 18,498
2014: 18,171
2006: 18,153
2012: 17,956
2019: 17,463
2011: 17,353
2015: 16,928
2016: 16,722
2023: 16,703
2022: 16,030
2010: 16,016
2008: 15,999
2004: 15,233
2018: 15,165
2009: 13,620
2017: 13,240
There were some sessions for which I could not find any data and obviously the arenas have different capacities, but ... pretty obvious that Chicago has drawn much better over the years than Indianapolis and even more obvious that the two times we have moved away from those central locations have been flops (at least as far as attendance goes.
Just for fun, I also wanted to look at what teams were in the semifinals or beyond for the BTTs with the top ten all-time average attendance numbers. I put the teams in order of my subjective opinion of which programs would most drive up the numbers in that given year:
#1. 2001 in Chicago, IL: Illinois, Indiana, Iowa, Penn State
#2. 2005 in Chicago, IL: Illinois, Wisconsin, Iowa, Minnesota
#3. 1998 in Chicago, IL: Illinois, Michigan, Purdue, Minnesota
#4. 2013 in Chicago, IL: Indiana, Michigan State, Wisconsin, Ohio State
#5. 2000 in Chicago, IL: Illinois, Michigan State, Wisconsin, Penn State
#6. 1999 in Chicago, IL: Illinois, Michigan State, Wisconsin, Ohio State
#7. 2002 in Indianapolis, IN: Indiana, Illinois, Ohio State, Iowa
#8. 2007 in Chicago, IL: Illinois, Wisconsin, Purdue, Ohio State
#9. 2003 in Chicago, IL: Illinois, Michigan State, Indiana, Ohio State
#10. 2014 in Indianapolis, IN: Michigan State, Ohio State, Michigan, Wisconsin
Notice a pattern? And for a comparison, here are the three lowest attendance years:
#22. 2018 in New York, NY: Michigan, Michigan State, Penn State, Purdue
#23. 2009 in Indianapolis, IN: Purdue,
Illinois, Michigan State, Ohio State
#24. 2017 in Washington, DC: Michigan, Wisconsin, Minnesota, Northwestern
Worth noting that Maryland lost its first game the DC year. 2009 is truly a head scratcher with all four teams playing through Saturday being programs that generally would theoretically travel well to Indy. I maintain that Chicago is the only location that can draw well no matter who is left in the tournament, though it appears clear that Illinois drives attendance here more than any one other school.