Detroit Pistons biggest year-to-year improvement/decline
based on regular season win percentage:

                            Change in 
                              win %
Improvement: 1949 -> 1950     0.221   (0.367 -> 0.588)
Decline:     1993 -> 1994    -0.244   (0.488 -> 0.244)
Last Year:   2007 -> 2008     0.074   (0.646 -> 0.720)