Year	Percent change (Units)
1981	13.997
1982	12.495
1983	19.692
1984	20.019
1985	37.430
1986	41.615
1987	47.028
1988	54.042
1989	128.294
1990	96.008
1991	99.651
1992	180.715
1993	128.105
1994	38.355
1995	45.980
1996	35.210
1997	18.581
1998	30.567
1999	20.633
2000	30.100
2001	18.678
2002	26.654
2003	17.161
2004	17.502
2005	15.851
2006	8.239
2007	8.933
2008	16.560
2009	9.900
2010	7.900
2011	7.200
2012	7.328
2013	7.140
2014	7.862
2015	21.112
2016	7.469
2017	6.085
2018	7.859
2019	11.719
2020	19.231
2021	16.354
2022	9.899
2023	13.000
2024	8.630
2025	7.000
2026	7.000
2027	7.000
2028	7.000
2029	7.000