Year	Percent change (Units)
1980	13.100
1981	19.318
1982	13.730
1983	9.598
1984	10.916
1985	10.231
1986	4.255
1987	9.556
1988	13.578
1989	13.546
1990	23.134
1991	14.473
1992	33.668
1993	54.700
1994	6.612
1995	6.890
1996	3.136
1997	9.808
1998	1.980
1999	10.503
2000	11.780
2001	1.602
2002	4.247
2003	8.350
2004	17.083
2005	4.912
2006	7.316
2007	5.600
2008	15.478
2009	8.016
2010	4.509
2011	18.934
2012	3.200
2013	7.149
2014	6.019
2015	8.007
2016	6.350
2017	4.496
2018	5.711
2019	7.157
2020	5.617
2021	5.725
2022	9.064
2023	6.636
2024	6.188
2025	5.236
2026	5.227
2027	5.038
2028	5.000
2029	5.000