Year	Percent change (Units)
1981	14.384
1982	37.831
1983	-1.964
1984	-7.925
1985	-8.569
1986	3.528
1987	-4.874
1988	-3.421
1989	2.865
1990	5.774
1991	223.966
1992	8.750
1993	13.410
1994	5.405
1995	3.846
1996	4.321
1997	3.550
1998	5.429
1999	3.523
2000	5.497
2001	3.226
2002	4.327
2003	2.995
2004	5.593
2005	7.203
2006	9.091
2007	7.609
2008	14.478
2009	1.324
2010	13.353
2011	5.250
2012	7.178
2013	5.675
2014	8.378
2015	1.586
2016	3.122
2017	1.325
2018	1.027
2019	0.370
2020	0.829
2021	3.470
2022	8.738
2023	0.731
2024	2.238
2025	2.107
2026	1.982
2027	1.927
2028	1.829
2029	1.809