New York Mets biggest year-to-year improvement/decline
based on regular season win percentage:

                            Change in 
                              win %
Improvement: 1968 -> 1969      16.6   (45.1  ->  61.7)
Decline:     1976 -> 1977     -13.6   (53.1  ->  39.5)
Last Year:   2006 -> 2007      -5.6   (59.9  ->  54.3)