Year	Percent change (Units)
1987	33.654
1988	26.259
1989	26.068
1990	27.331
1991	12.233
1992	16.100
1993	4.996
1994	2.543
1995	5.200
1996	2.053
1997	5.291
1998	4.529
1999	6.161
2000	7.207
2001	1.130
2002	6.118
2003	12.094
2004	27.644
2005	29.663
2006	39.132
2007	12.822
2008	13.504
2009	7.899
2010	20.803
2011	19.026
2012	12.833
2013	10.548
2014	8.968
2015	7.324
2016	8.701
2017	9.546
2018	9.942
2019	9.122
2020	10.579
2021	12.535
2022	8.613
2023	9.265
2024	11.500
2025	10.800
2026	9.700
2027	9.700
2028	9.700
2029	7.500