Year	Percent change (Units)
1981	-0.592
1982	4.833
1983	20.796
1984	14.340
1985	8.319
1986	7.979
1987	10.135
1988	8.632
1989	18.697
1990	12.976
1991	0.451
1992	5.445
1993	1.304
1994	10.465
1995	13.588
1996	5.711
1997	2.022
1998	15.097
1999	0.056
2000	-3.856
2001	4.038
2002	9.948
2003	17.499
2004	6.118
2005	-5.129
2006	11.228
2007	13.691
2008	0.150
2009	-14.992
2010	-1.680
2011	9.313
2012	-2.869
2013	12.379
2014	5.313
2015	6.341
2016	4.191
2017	7.966
2018	4.150
2019	3.978
2020	-18.834
2021	12.282
2022	17.580
2023	4.057
2024	2.775
2025	2.031
2026	1.976
2027	2.002
2028	1.849
2029	1.812