Year	Percent change (Units)
1981	10.305
1982	8.264
1983	-32.614
1984	25.639
1985	-10.905
1986	27.764
1987	37.273
1988	14.657
1989	-29.958
1990	14.541
1991	71.931
1992	-56.816
1993	23.403
1994	45.619
1995	-45.380
1996	148.730
1997	-35.361
1998	19.174
1999	5.508
2000	-33.617
2001	-33.266
2002	63.516
2003	-1.077
2004	-9.575
2005	106.772
2006	159.369
2007	37.784
2008	56.302
2009	-29.225
2010	42.978
2011	-30.240
2012	22.548
2013	-17.430
2014	-8.497
2015	-15.835
2016	-5.065
2017	-6.458
2018	16.046
2019	-22.889
2020	-6.577
2021	24.272
2022	-50.501
2023	-11.810
2024	-0.316
2025	9.280
2026	-6.173
2027	0.770
2028	3.870
2029	-1.063