Year	Percent change (Units)
1980	9.286
1981	4.511
1982	7.016
1983	6.403
1984	8.651
1985	7.007
1986	5.292
1987	8.682
1988	15.788
1989	16.950
1990	28.970
1991	34.234
1992	22.950
1993	22.451
1994	18.866
1995	28.303
1996	23.455
1997	18.295
1998	14.227
1999	9.973
2000	9.788
2001	9.151
2002	5.261
2003	4.665
2004	6.750
2005	3.562
2006	3.904
2007	7.952
2008	6.056
2009	4.198
2010	4.872
2011	3.929
2012	5.661
2013	1.713
2014	-0.229
2015	-0.066
2016	0.397
2017	2.354
2018	2.839
2019	3.373
2020	3.305
2021	5.105
2022	14.620
2023	17.140
2024	3.723
2025	3.549
2026	2.909
2027	3.000
2028	3.000
2029	3.000