Year	Percent change (Units)
1981	100.222
1982	16.787
1983	142.418
1984	5.988
1985	19.499
1986	33.335
1987	34.164
1988	26.571
1989	30.458
1990	35.902
1991	10.261
1992	13.330
1993	27.656
1994	34.179
1995	70.817
1996	26.123
1997	22.141
1998	15.752
1999	13.791
2000	40.540
2001	21.288
2002	15.171
2003	23.563
2004	11.777
2005	14.838
2006	10.923
2007	12.748
2008	18.133
2009	9.459
2010	6.868
2011	8.372
2012	8.124
2013	13.495
2014	16.987
2015	17.692
2016	15.362
2017	11.821
2018	9.425
2019	7.759
2020	10.473
2021	12.621
2022	52.054
2023	23.158
2024	15.012
2025	8.000
2026	8.000
2027	8.000
2028	8.000
2029	8.000