Year	Percent change (Units)
1981	48.737
1982	13.751
1983	2.797
1984	10.159
1985	-5.045
1986	33.503
1987	-8.433
1988	5.970
1989	3.356
1990	-16.661
1991	13.231
1992	5.248
1993	-16.839
1994	-43.595
1995	57.914
1996	12.195
1997	1.716
1998	-4.197
1999	-4.799
2000	70.084
2001	8.361
2002	6.357
2003	5.076
2004	15.907
2005	4.566
2006	11.185
2007	30.732
2008	34.076
2009	-23.114
2010	33.636
2011	95.127
2012	1.786
2013	-3.255
2014	-17.469
2015	-11.195
2016	-5.890
2017	20.456
2018	28.790
2019	5.757
2020	-5.318
2021	5.837
2022	9.609
2023	16.392
2024	8.635
2025	10.481
2026	8.895
2027	5.207
2028	4.807
2029	3.147