Year	Percent change (Units)
1980	9.619
1981	12.523
1982	-0.175
1983	-8.113
1984	0.963
1985	16.568
1986	15.007
1987	-8.557
1988	1.977
1989	-14.713
1990	-13.606
1991	3.457
1992	1.819
1993	20.465
1994	29.422
1995	-51.056
1996	4.701
1997	36.394
1998	-5.487
1999	4.264
2000	-22.487
2001	3.641
2002	9.623
2003	2.091
2004	12.402
2005	21.340
2006	26.162
2007	31.556
2008	28.771
2009	20.711
2010	4.169
2011	15.611
2012	29.123
2013	-0.806
2014	10.000
2015	12.423
2016	-5.304
2017	12.627
2018	10.678
2019	8.567
2020	2.775
2021	3.984
2022	12.983
2023	17.903
2024	2.832
2025	3.302
2026	4.363
2027	4.423
2028	2.834
2029	2.802