Year	Percent change (Units)
1980	32.922
1981	20.762
1982	24.988
1983	-5.672
1984	14.124
1985	15.717
1986	-34.030
1987	-30.995
1988	9.564
1989	0.900
1990	11.200
1991	17.004
1992	17.821
1993	13.654
1994	-12.780
1995	4.449
1996	2.206
1997	11.041
1998	17.215
1999	-13.654
2000	7.040
2001	17.520
2002	6.006
2003	2.676
2004	17.854
2005	-5.242
2006	13.997
2007	35.467
2008	27.860
2009	-19.956
2010	-5.040
2011	10.285
2012	24.078
2013	27.444
2014	-8.027
2015	7.964
2016	-16.997
2017	8.401
2018	-3.354
2019	-16.615
2020	22.420
2021	-5.917
2022	18.236
2023	4.736
2024	11.839
2025	1.140
2026	1.448
2027	1.340
2028	0.665
2029	3.510