Year	Percent change (Units)
1980	13.049
1981	16.387
1982	16.258
1983	48.434
1984	31.230
1985	27.983
1986	23.030
1987	29.504
1988	58.216
1989	75.648
1990	48.519
1991	48.804
1992	54.341
1993	45.000
1994	27.443
1995	22.886
1996	24.400
1997	30.600
1998	36.100
1999	52.200
2000	96.100
2001	37.674
2002	12.485
2003	7.929
2004	2.741
2005	2.170
2006	3.299
2007	2.276
2008	8.400
2009	5.160
2010	3.554
2011	4.475
2012	5.102
2013	2.722
2014	3.589
2015	3.966
2016	1.728
2017	0.417
2018	-0.224
2019	0.266
2020	-0.339
2021	0.133
2022	3.466
2023	2.216
2024	1.367
2025	1.548
2026	1.458
2027	1.463
2028	1.463
2029	1.463