Year	Percent change (Units)
1980	18.140
1981	13.856
1982	-2.753
1983	14.805
1984	22.100
1985	5.568
1986	15.257
1987	33.509
1988	26.771
1989	10.431
1990	9.514
1991	17.316
1992	19.820
1993	13.614
1994	9.985
1995	11.407
1996	4.569
1997	6.023
1998	-4.568
1999	3.632
2000	18.535
2001	-1.794
2002	8.365
2003	14.862
2004	15.644
2005	12.416
2006	10.236
2007	6.875
2008	3.241
2009	-11.255
2010	18.031
2011	4.631
2012	3.305
2013	8.211
2014	0.840
2015	-1.726
2016	1.558
2017	6.451
2018	3.466
2019	-5.452
2020	-1.402
2021	18.719
2022	-13.953
2023	-10.301
2024	5.322
2025	4.290
2026	4.138
2027	4.184
2028	4.106
2029	4.164