Year	Percent change (Units)
1980	21.800
1981	19.510
1982	16.460
1983	14.700
1984	10.740
1985	8.969
1986	5.820
1987	4.720
1988	5.090
1989	6.245
1990	6.395
1991	6.215
1992	4.982
1993	4.499
1994	4.167
1995	5.387
1996	3.985
1997	1.849
1998	2.031
1999	1.651
2000	2.580
2001	2.324
2002	2.612
2003	2.813
2004	2.257
2005	2.207
2006	2.229
2007	2.025
2008	3.492
2009	0.765
2010	1.620
2011	2.935
2012	3.315
2013	1.245
2014	0.234
2015	0.108
2016	-0.050
2017	1.326
2018	1.243
2019	0.634
2020	-0.145
2021	1.941
2022	8.736
2023	5.903
2024	1.673
2025	2.000
2026	2.000
2027	2.000
2028	2.000
2029	2.000