Year	Percent change (Units)
1981	-0.514
1982	-1.283
1983	1.758
1984	3.118
1985	2.656
1986	3.126
1987	1.850
1988	4.585
1989	4.481
1990	4.178
1991	2.451
1992	1.589
1993	1.264
1994	3.009
1995	2.773
1996	3.494
1997	4.328
1998	4.668
1999	5.032
2000	4.199
2001	2.328
2002	0.217
2003	0.158
2004	1.983
2005	2.047
2006	3.462
2007	3.772
2008	2.172
2009	-3.667
2010	1.341
2011	1.550
2012	-1.031
2013	-0.127
2014	1.424
2015	1.958
2016	2.192
2017	2.911
2018	2.361
2019	1.956
2020	-3.885
2021	6.192
2022	4.326
2023	0.093
2024	0.632
2025	1.296
2026	1.909
2027	1.919
2028	1.765
2029	1.630