Year	Percent change (Units)
1980	39.985
1981	35.000
1982	29.915
1983	30.263
1984	26.010
1985	19.038
1986	64.700
1987	36.890
1988	27.291
1989	28.256
1990	25.694
1991	19.682
1992	16.559
1993	7.135
1994	4.220
1995	5.554
1996	2.986
1997	1.937
1998	5.103
1999	4.554
2000	6.766
2001	5.377
2002	2.960
2003	11.036
2004	17.463
2005	31.358
2006	34.702
2007	22.861
2008	18.367
2009	4.682
2010	15.466
2011	21.351
2012	15.227
2013	11.887
2014	9.712
2015	8.151
2016	8.174
2017	8.914
2018	9.826
2019	9.471
2020	10.602
2021	12.597
2022	10.499
2023	7.800
2024	11.034
2025	10.180
2026	9.665
2027	9.175
2028	8.740
2029	8.600