Year	Percent change (Units)
1980	13.329
1981	9.186
1982	-5.417
1983	-7.335
1984	-15.310
1985	-4.672
1986	-14.793
1987	4.305
1988	6.073
1989	18.711
1990	17.000
1991	16.190
1992	25.298
1993	14.262
1994	8.371
1995	14.036
1996	3.412
1997	17.551
1998	1.975
1999	1.621
2000	9.163
2001	9.846
2002	13.019
2003	13.672
2004	24.479
2005	12.664
2006	8.805
2007	38.004
2008	19.315
2009	-13.885
2010	-1.465
2011	9.809
2012	10.536
2013	10.739
2014	13.202
2015	3.129
2016	3.680
2017	0.685
2018	-0.150
2019	-3.033
2020	-17.988
2021	7.159
2022	14.055
2023	9.956
2024	2.791
2025	3.010
2026	2.937
2027	3.469
2028	3.704
2029	4.429