Year	Percent change (Units)
1980	40.557
1981	22.330
1982	-2.456
1983	-28.994
1984	-20.714
1985	-16.512
1986	32.338
1987	8.191
1988	-15.726
1989	-25.212
1990	0.000
1991	23.064
1992	5.113
1993	3.259
1994	30.587
1995	28.427
1996	-1.384
1997	13.203
1998	2.416
1999	-18.045
2000	4.200
2001	0.971
2002	4.332
2003	3.529
2004	7.638
2005	10.410
2006	15.452
2007	20.670
2008	24.598
2009	-17.486
2010	27.198
2011	13.477
2012	10.352
2013	3.818
2014	-1.620
2015	0.182
2016	-3.015
2017	4.493
2018	1.359
2019	-0.157
2020	-11.034
2021	18.466
2022	2.448
2023	-4.355
2024	4.644
2025	3.721
2026	2.573
2027	2.491
2028	2.327
2029	1.960