San Antonio Spurs biggest year-to-year improvement/decline
based on regular season win percentage:

                            Change in 
                              win %
Improvement: 1997 -> 1998     0.439   (0.244 -> 0.683)
Decline:     1996 -> 1997    -0.476   (0.720 -> 0.244)
Last Year:   2007 -> 2008    -0.024   (0.707 -> 0.683)