Year	Percent change (Units)
1980	14.945
1981	0.747
1982	-8.625
1983	-22.541
1984	6.158
1985	12.145
1986	4.419
1987	4.729
1988	-22.307
1989	20.487
1990	-7.900
1991	14.951
1992	19.312
1993	9.506
1994	10.103
1995	5.534
1996	10.775
1997	8.934
1998	18.540
1999	-1.505
2000	-13.643
2001	-5.121
2002	-2.263
2003	-1.690
2004	13.764
2005	7.085
2006	7.398
2007	20.907
2008	16.400
2009	-15.021
2010	27.151
2011	27.510
2012	-3.626
2013	-3.282
2014	-2.104
2015	-3.073
2016	0.858
2017	6.973
2018	-0.579
2019	-10.306
2020	-27.777
2021	32.621
2022	28.590
2023	-9.944
2024	10.261
2025	8.667
2026	4.257
2027	0.935
2028	4.352
2029	3.971