Year	Percent change (Units)
1980	13.858
1981	11.603
1982	20.667
1983	11.398
1984	10.284
1985	13.007
1986	2.534
1987	8.638
1988	12.265
1989	13.789
1990	17.782
1991	20.084
1992	27.332
1993	45.979
1994	28.814
1995	1.554
1996	6.814
1997	11.322
1998	5.416
1999	5.779
2000	9.975
2001	5.732
2002	1.966
2003	9.805
2004	11.795
2005	9.912
2006	6.032
2007	4.271
2008	15.114
2009	10.537
2010	4.084
2011	14.022
2012	9.378
2013	5.717
2014	6.878
2015	6.582
2016	6.318
2017	7.985
2018	4.690
2019	5.240
2020	5.290
2021	6.109
2022	7.648
2023	7.675
2024	6.601
2025	5.488
2026	5.303
2027	4.851
2028	5.000
2029	5.000