Philadelphia Phillies : biggest year-to-year improvement/decline

Based on regular season win percentage:

                            Change in 
                              win %
Improvement: 1904 -> 1905      20.4   (34.2  ->  54.6)
Decline:     2011 -> 2012     -13.0   (63.0  ->  50.0)
Last Year:   2019 -> 2020      -3.3   (50.0  ->  46.7)