Year	Percent change (Units)
1980	17.470
1981	14.332
1982	11.635
1983	15.175
1984	13.335
1985	7.623
1986	7.694
1987	10.752
1988	7.758
1989	11.432
1990	11.064
1991	3.800
1992	6.486
1993	10.791
1994	8.814
1995	5.272
1996	3.286
1997	3.662
1998	5.603
1999	3.414
2000	3.524
2001	5.602
2002	4.142
2003	3.781
2004	3.757
2005	6.878
2006	8.308
2007	7.875
2008	12.036
2009	7.010
2010	10.537
2011	5.091
2012	9.280
2013	5.189
2014	5.698
2015	4.659
2016	3.069
2017	1.884
2018	1.019
2019	1.001
2020	0.599
2021	2.061
2022	5.826
2023	4.629
2024	1.484
2025	2.173
2026	2.045
2027	1.954
2028	1.878
2029	1.819