Year	Percent change (Units)
1981	-16.967
1982	-28.292
1983	-19.389
1984	-14.481
1985	7.418
1986	28.664
1987	16.461
1988	-32.295
1989	19.042
1990	32.510
1991	-12.688
1992	-2.628
1993	31.932
1994	3.630
1995	0.934
1996	28.341
1997	-61.368
1998	13.704
1999	42.934
2000	29.181
2001	16.993
2002	18.996
2003	5.246
2004	-18.949
2005	11.039
2006	-6.707
2007	-4.000
2008	7.028
2009	42.008
2010	43.147
2011	104.135
2012	-2.158
2013	-6.713
2014	30.031
2015	-10.566
2016	-31.807
2017	8.144
2018	-4.692
2019	15.702
2020	-17.644
2021	19.999
2022	-6.479
2023	5.145
2024	10.020
2025	-0.983
2026	1.431
2027	3.377
2028	3.825
2029	3.992