Year	Percent change (Units)
1981	5.349
1982	3.540
1983	6.669
1984	6.635
1985	5.208
1986	-2.226
1987	4.749
1988	6.452
1989	1.210
1990	-5.343
1991	-13.877
1992	2.102
1993	-10.139
1994	13.720
1995	36.499
1996	9.202
1997	22.755
1998	15.544
1999	11.798
2000	24.945
2001	8.822
2002	5.725
2003	6.257
2004	17.887
2005	12.875
2006	19.518
2007	16.104
2008	6.692
2009	-10.724
2010	11.118
2011	6.408
2012	-1.704
2013	4.103
2014	9.198
2015	7.365
2016	3.804
2017	6.475
2018	4.985
2019	5.424
2020	-6.148
2021	8.277
2022	12.607
2023	7.136
2024	3.300
2025	5.000
2026	5.500
2027	5.600
2028	5.600
2029	5.600