Year	Percent change (Units)
1980	6.381
1981	16.323
1982	12.257
1983	8.509
1984	10.548
1985	11.676
1986	11.636
1987	10.373
1988	8.759
1989	8.054
1990	10.248
1991	6.585
1992	1.718
1993	3.489
1994	7.155
1995	11.201
1996	1.642
1997	5.592
1998	6.767
1999	7.785
2000	2.288
2001	2.162
2002	2.446
2003	4.382
2004	8.819
2005	7.348
2006	7.540
2007	9.197
2008	10.032
2009	2.243
2010	8.702
2011	10.044
2012	5.546
2013	8.049
2014	6.966
2015	6.253
2016	5.531
2017	5.944
2018	5.542
2019	5.518
2020	6.021
2021	5.642
2022	7.563
2023	9.745
2024	7.900
2025	6.000
2026	5.500
2027	5.500
2028	5.500
2029	5.500