Year	Percent change (Units)
1981	-22.029
1982	0.320
1983	-5.524
1984	10.612
1985	-9.441
1986	15.636
1987	-1.261
1988	-27.386
1989	13.849
1990	15.216
1991	3.922
1992	11.321
1993	11.263
1994	15.712
1995	2.269
1996	5.665
1997	-13.766
1998	17.149
1999	8.078
2000	-0.072
2001	39.668
2002	2.473
2003	-36.226
2004	-5.839
2005	36.733
2006	-4.769
2007	6.372
2008	41.167
2009	-10.624
2010	-11.021
2011	14.063
2012	7.237
2013	-10.055
2014	-1.425
2015	-7.684
2016	-31.920
2017	-9.658
2018	-5.945
2019	14.754
2020	-30.628
2021	30.152
2022	21.612
2023	11.962
2024	19.789
2025	7.103
2026	7.155
2027	6.392
2028	7.333
2029	6.801