Year	Percent change (Units)
1980	9.900
1981	17.051
1982	7.563
1983	6.844
1984	7.468
1985	8.107
1986	6.791
1987	-2.153
1988	-7.865
1989	-1.770
1990	-6.161
1991	-3.764
1992	-3.050
1993	-3.158
1994	-2.495
1995	3.304
1996	4.912
1997	5.314
1998	4.895
1999	4.062
2000	3.363
2001	3.356
2002	4.847
2003	4.994
2004	6.561
2005	1.218
2006	3.524
2007	4.100
2008	2.858
2009	2.619
2010	2.935
2011	3.484
2012	4.508
2013	4.987
2014	5.779
2015	5.600
2016	4.479
2017	3.541
2018	4.022
2019	3.422
2020	0.539
2021	3.649
2022	3.595
2023	3.969
2024	4.253
2025	4.468
2026	4.458
2027	4.511
2028	4.573
2029	4.530