I was watching and listening to this review (https://youtu.be/jjKh8ioa5qM) of Tony Danza's feature film from 1989, She's Out of Control (https://en.wikipedia.org/wiki/She%27s_Out_of_Control). It was at one point in the review, noted that Who's the Boss' ratings after that film was released in April 1989, coincidentally started to go down. I went to look just to make sure, and according to Wikipedia (https://en.wikipedia.org/wiki/Who%27s_the_Boss%3F#Episodes), Who's the Boss? was a top ten rated show for its second-fifth seasons (1985-89). It was the sixth highest rated (http://www.thetvratingsguide.com/1991/08/1987-88-ratings-history.html) show on TV in 1987-88 (https://en.wikipedia.org/wiki/Top-rated_United_States_television_programs_of_1987%E2%80%9388) and the seventh highest rated (http://www.thetvratingsguide.com/1991/08/written-protesting-program-preemptions.html) show the following season (https://en.wikipedia.org/wiki/Top-rated_United_States_television_programs_of_1988%E2%80%9389).

Season 6 (1989-90 (http://www.thetvratingsguide.com/1991/08/1989-90-ratings-history.html)) was the first season since the first one (1984-85) that Who's the Boss? didn't crack the top ten in the Nielsen ratings (https://en.wikipedia.org/wiki/Top-rated_United_States_television_programs_of_1989%E2%80%9390) (it finished at #12 (https://www.classic-tv.com/features/ratings/1989-1990-tv-show-ratings)). The following season (https://en.wikipedia.org/wiki/Top-rated_United_States_television_programs_of_1990%E2%80%9391), it slid down (http://www.thetvratingsguide.com/1991/08/written-torn-between-cosbys-simpsons-by.html) to 19th place and for its eighth and final year, Who's the Boss? was ranked at 76th place (http://www.thetvratingsguide.com/1991/08/1991-92-ratings-history.html). In fairness, if I remember correctly, ABC moved Who's the Boss? (https://www.tvtango.com/series/whos_the_boss_1984/episodes?page=4) to a Saturday night (https://en.wikipedia.org/wiki/TGIF_(TV_programming_block)#I_Love_Saturday_Night_(1992)) timeslot for its final year (1991-92).

12 and 19 are still strong ratings inside the top 20. Who's the Boss? didn't tumble until moved to Saturdays.

Why did Who's the Boss move from Tuesdays to Saturdays to make room for Full House (which itself had relocated from Fridays)? Two simple reasons:

1. Creative exhaustion
2. An abundance of newer and fresher sitcoms on the ABC schedule

Why did Who's the Boss move from Tuesdays to Saturdays to make room for Full House (which itself had relocated from Fridays)? Two simple reasons:

1. Creative exhaustion
2. An abundance of newer and fresher sitcoms on the ABC schedule

Some ABC promos (https://youtu.be/0_ewx5ehS1Y?t=176) for Who's the Boss? on Saturday (https://youtu.be/F3uOHdqHUSw?t=218) nights (https://youtu.be/cLweFzo6T7k?t=803) circa 1991 (https://youtu.be/LsR8mi5W2dE?t=571)-92:
AGiJT2zTpIE

UICldAJ9X4c

oZeGmmN6Ezc

25yGZ0MgrH4

ZviYnLFIrKU

o3gE0_I_TXw

12 and 19 are still strong ratings inside the top 20. Who's the Boss? didn't tumble until moved to Saturdays.

I read on the Who's the Boss? subreddit (https://www.reddit.com/r/WhosTheBossSitcom/comments/1ivpccc/i_nearly_gave_up_on_the_show_at_the_end_of_season/) that the ratings didn't really start to go down significantly or noticeably until the end of Season 6. It really began (https://www.reddit.com/r/WhosTheBossSitcom/comments/1jichln/comment/mo6j7mc/) with the "All-Nighter" (http://reviewingeverytvshowiown.blogspot.com/2017/05/whos-boss-all-nighter.html) episode (https://www.reddit.com/r/WhosTheBossSitcom/comments/1duhqfl/how_do_you_guys_feel_about_the_season_6_finale/), when Tony impulsively slept with Kathleen. From there, the ratings went down in Seasons 7 and 8 because the producers alienated a large percentage of their audience.