Year	Percent change (Units)
1981	5.556
1982	0.590
1983	-8.452
1984	-1.857
1985	-16.010
1986	10.666
1987	12.785
1988	-1.057
1989	-3.847
1990	1.345
1991	-13.143
1992	-2.998
1993	0.376
1994	-2.761
1995	15.227
1996	6.006
1997	-0.965
1998	-28.023
1999	-13.431
2000	4.475
2001	-37.198
2002	-34.445
2003	-8.565
2004	113.569
2005	-31.522
2006	32.974
2007	-72.729
2008	156.964
2009	6.216
2010	3.045
2011	3.470
2012	3.720
2013	1.632
2014	-0.213
2015	-2.410
2016	-1.558
2017	0.907
2018	10.607
2019	255.292
2020	557.210
2021	98.546
2022	193.399
2023	667.361
2024	560.981
2025	554.653
2026	511.536
2027	480.492
2028	450.898
2029	400.000