Year	Percent change (Units)
1980	26.471
1981	28.034
1982	59.115
1983	101.805
1984	65.439
1985	57.789
1986	86.449
1987	131.960
1988	113.502
1989	19.919
1990	26.650
1991	22.609
1992	15.517
1993	9.763
1994	6.986
1995	35.061
1996	34.350
1997	20.597
1998	15.917
1999	16.566
2000	9.486
2001	6.366
2002	5.037
2003	4.550
2004	4.694
2005	3.990
2006	3.633
2007	3.969
2008	5.130
2009	5.296
2010	4.155
2011	3.404
2012	4.111
2013	3.804
2014	4.019
2015	2.719
2016	2.820
2017	6.042
2018	4.898
2019	3.635
2020	3.398
2021	5.693
2022	7.898
2023	5.525
2024	4.020
2025	3.289
2026	3.003
2027	3.000
2028	3.000
2029	3.000