Year	Percent change (Units)
1980	1.523
1981	2.200
1982	16.928
1983	4.686
1984	-0.320
1985	-0.200
1986	0.700
1987	1.100
1988	2.600
1989	0.900
1990	127.900
1991	161.121
1992	210.386
1993	256.105
1994	136.742
1995	32.272
1996	38.809
1997	154.763
1998	59.097
1999	45.804
2000	45.667
2001	34.454
2002	22.498
2003	15.370
2004	11.855
2005	8.995
2006	6.591
2007	4.834
2008	7.846
2009	5.584
2010	6.113
2011	5.795
2012	3.339
2013	4.002
2014	1.076
2015	-0.596
2016	-1.555
2017	1.344
2018	4.631
2019	3.825
2020	2.646
2021	5.046
2022	13.800
2023	10.397
2024	6.049
2025	4.048
2026	3.330
2027	2.956
2028	3.041
2029	3.016