Boston Celtics biggest year-to-year improvement/decline

Based on regular season win percentage:

                            Change in 
                              win %
Improvement: 2007 -> 2008     0.512   (0.293 -> 0.805)
Decline:     1996 -> 1997    -0.219   (0.402 -> 0.183)
Last Year:   2025 -> 2026    -0.061   (0.744 -> 0.683)