Year	Percent change (Units)
1980	17.984
1981	9.172
1982	6.830
1983	16.657
1984	31.255
1985	29.700
1986	24.400
1987	11.200
1988	8.200
1989	16.120
1990	24.779
1991	51.021
1992	77.287
1993	21.635
1994	35.543
1995	19.910
1996	26.405
1997	9.658
1998	8.632
1999	5.951
2000	8.070
2001	6.881
2002	6.992
2003	10.131
2004	13.521
2005	15.099
2006	8.520
2007	9.287
2008	22.026
2009	9.576
2010	12.616
2011	7.522
2012	6.892
2013	9.360
2014	8.275
2015	3.681
2016	2.350
2017	4.378
2018	3.740
2019	3.910
2020	5.210
2021	5.882
2022	10.347
2023	6.471
2024	7.000
2025	5.000
2026	5.040
2027	5.020
2028	5.000
2029	5.000