Year	Percent change (Units)
1980	24.672
1981	18.270
1982	5.388
1983	21.435
1984	9.482
1985	1.482
1986	9.074
1987	10.167
1988	15.030
1989	15.103
1990	19.622
1991	9.015
1992	13.815
1993	10.320
1994	4.210
1995	11.512
1996	16.801
1997	10.741
1998	3.724
1999	3.984
2000	10.837
2001	10.817
2002	11.289
2003	12.182
2004	13.075
2005	7.650
2006	13.452
2007	18.568
2008	13.962
2009	5.132
2010	6.772
2011	4.867
2012	9.283
2013	4.633
2014	1.353
2015	4.612
2016	4.408
2017	7.111
2018	2.801
2019	4.844
2020	4.235
2021	12.096
2022	54.530