Year	Percent change (Units)
1981	-2.934
1982	5.953
1983	-12.961
1984	-11.068
1985	26.081
1986	19.984
1987	0.825
1988	-0.426
1989	-15.355
1990	11.709
1991	1.703
1992	-12.130
1993	7.908
1994	-29.191
1995	15.578
1996	7.495
1997	-1.990
1998	28.513
1999	-15.680
2000	-12.360
2001	2.304
2002	7.666
2003	24.521
2004	-5.831
2005	2.687
2006	3.034
2007	14.221
2008	10.570
2009	-2.440
2010	13.986
2011	10.532
2012	13.171
2013	13.528
2014	-6.417
2015	8.450
2016	2.235
2017	13.012
2018	3.512
2019	-2.652
2020	-2.303
2021	11.369
2022	0.484
2023	4.012
2024	4.761
2025	3.762
2026	3.940
2027	4.189
2028	4.349
2029	4.507