Year	Percent change (Units)
1980	4.997
1981	10.042
1982	5.460
1983	-9.819
1984	22.058
1985	3.790
1986	-3.149
1987	2.516
1988	21.000
1989	21.162
1990	-4.212
1991	-2.243
1992	6.706
1993	5.136
1994	14.591
1995	8.747
1996	7.455
1997	10.837
1998	7.294
1999	8.367
2000	8.006
2001	-5.053
2002	11.034
2003	11.356
2004	15.202
2005	9.638
2006	8.673
2007	12.877
2008	10.745
2009	-8.838
2010	16.169
2011	10.532
2012	6.176
2013	-2.281
2014	-1.400
2015	2.259
2016	0.122
2017	7.809
2018	4.277
2019	-0.725
2020	-11.983
2021	4.803
2022	12.787
2023	3.338
2024	3.346
2025	2.902
2026	2.408
2027	2.422
2028	2.422
2029	2.422