Year	Percent change (Units)
1980	15.429
1981	16.337
1982	8.085
1983	13.126
1984	50.826
1985	5.656
1986	-0.336
1987	7.047
1988	9.566
1989	15.248
1990	18.178
1991	13.305
1992	7.576
1993	7.042
1994	10.855
1995	8.309
1996	7.397
1997	6.378
1998	10.072
1999	3.922
2000	8.595
2001	3.668
2002	2.048
2003	2.372
2004	7.130
2005	5.990
2006	4.239
2007	3.464
2008	7.860
2009	4.453
2010	3.618
2011	4.239
2012	2.871
2013	3.721
2014	1.906
2015	0.770
2016	2.183
2017	2.885
2018	5.296
2019	2.367
2020	3.276
2021	3.078
2022	8.054
2023	3.936
2024	3.247
2025	3.000
2026	3.000
2027	3.000
2028	3.000
2029	3.000