Year	Percent change (Units)
1980	0.216
1981	11.483
1982	0.400
1983	7.000
1984	3.200
1985	0.100
1986	13.900
1987	25.000
1988	44.277
1989	42.886
1990	42.248
1991	46.480
1992	33.697
1993	25.500
1994	51.160
1995	36.800
1996	42.047
1997	69.049
1998	42.105
1999	11.011
2000	11.011
2001	9.219
2002	10.130
2003	9.793
2004	13.285
2005	17.152
2006	23.075
2007	18.550
2008	31.991
2009	16.957
2010	13.339
2011	14.321
2012	10.638
2013	8.106
2014	6.988
2015	6.130
2016	5.407
2017	5.690
2018	7.873
2019	7.716
2020	9.820
2021	8.138
2022	18.006
2023	21.184
2024	14.191
2025	7.849
2026	5.073
2027	5.003
2028	5.036
2029	5.004