The Cubs finished 2018 with a total of 3,181,089 tickets sold at Wrigley Field. That’s down 18,473 from 2017 — but with a catch, the tiebreaker game played October 1 is considered a regular-season game, so the 38,450 who paid for that game are counted in the 2018 total.
Thus, the year-by-year comparison is more accurate at this number, 3,142,639, or 56,923 down for the first 81 dates of both seasons. That’s a drop of 703 per date, which is really pretty insignificant. (The average drop is 707 per date including the tiebreaker.)
Overall, MLB attendance dropped by 1,188 per date from 2017 to 2018.