Denver Broncos : biggest year-to-year improvement/decline

Based on regular season win percentage:

                            Change in 
                              win %
Improvement: 1990 -> 1991     0.438   (0.312 -> 0.750)
Decline:     1998 -> 1999    -0.500   (0.875 -> 0.375)
Last Year:   2019 -> 2020    -0.125   (0.438 -> 0.313)