Year	Percent change (Units)
1980	0.931
1981	13.264
1982	-6.019
1983	46.616
1984	-10.667
1985	-20.295
1986	-27.501
1987	6.255
1988	-21.301
1989	19.497
1990	34.700
1991	33.097
1992	-9.101
1993	-19.637
1994	-39.040
1995	-0.928
1996	16.759
1997	-6.460
1998	0.356
1999	-5.271
2000	10.320
2001	23.154
2002	31.833
2003	21.169
2004	12.613
2005	2.818
2006	6.582
2007	8.631
2008	11.316
2009	5.436
2010	0.142
2011	-6.753
2012	-11.799
2013	-4.766
2014	16.116
2015	-6.378
2016	12.690
2017	9.447
2018	-16.667
2019	-4.816
2020	-27.284
2021	20.625
2022	6.728
2023	-2.191
2024	-6.435
2025	-9.213
2026	-9.884
2027	-10.240
2028	-10.646
2029	-10.300