Year	Percent change (Units)
1980	4.444
1981	9.479
1982	11.016
1983	9.923
1984	8.549
1985	3.556
1986	3.575
1987	5.671
1988	7.830
1989	10.219
1990	10.318
1991	11.192
1992	9.586
1993	8.796
1994	8.816
1995	9.034
1996	6.324
1997	5.818
1998	2.827
1999	-3.967
2000	-3.723
2001	-1.610
2002	-3.046
2003	-2.587
2004	-0.367
2005	0.914
2006	2.000
2007	2.035
2008	4.303
2009	0.579
2010	2.293
2011	5.305
2012	4.054
2013	4.338
2014	4.424
2015	2.991
2016	2.409
2017	1.494
2018	2.406
2019	2.883
2020	0.251
2021	1.569
2022	1.881
2023	2.097
2024	2.300
2025	2.250
2026	2.400
2027	2.500
2028	2.500
2029	2.500