Year	Percent change (Units)
1980	18.278
1981	30.457
1982	31.907
1983	19.469
1984	9.720
1985	10.566
1986	14.492
1987	15.461
1988	26.338
1989	9.017
1990	11.859
1991	8.540
1992	14.567
1993	9.990
1994	38.992
1995	49.036
1996	19.761
1997	4.492
1998	6.210
1999	7.189
2000	11.570
2001	7.917
2002	16.499
2003	-1.704
2004	13.956
2005	18.364
2006	10.766
2007	10.288
2008	9.297
2009	8.954
2010	9.247
2011	9.483
2012	5.714
2013	5.826
2014	6.080
2015	7.404
2016	6.056
2017	8.590
2018	8.598
2019	5.623
2020	4.188
2021	5.819
2022	8.157
2023	9.861
2024	7.789
2025	7.342
2026	6.894
2027	6.447
2028	6.000
2029	5.950