Year	Percent change (Units)
1980	5.721
1981	5.656
1982	-2.851
1983	-10.785
1984	6.894
1985	8.408
1986	7.699
1987	25.021
1988	-5.455
1989	-10.889
1990	0.306
1991	4.892
1992	-4.850
1993	-12.670
1994	7.490
1995	6.471
1996	16.620
1997	5.817
1998	23.580
1999	2.599
2000	3.646
2001	-11.237
2002	-2.878
2003	7.619
2004	17.704
2005	24.704
2006	16.282
2007	-5.699
2008	-18.913
2009	-25.237
2010	-0.407
2011	6.795
2012	2.280
2013	-0.256
2014	9.837
2015	18.798
2016	14.023
2017	11.294
2018	-3.217
2019	-7.735
2020	-11.075
2021	18.936
2022	10.659
2023	-2.640
2024	1.342
2025	1.842
2026	2.387
2027	2.656
2028	2.812
2029	2.818