Year	Percent change (Units)
1981	13.413
1982	-14.020
1983	-12.197
1984	18.604
1985	12.178
1986	-2.635
1987	17.920
1988	-9.618
1989	-29.793
1990	37.563
1991	5.678
1992	-15.291
1993	8.909
1994	-3.094
1995	-13.806
1996	5.594
1997	-1.268
1998	49.119
1999	-9.511
2000	4.376
2001	-2.263
2002	30.081
2003	1.613
2004	22.043
2005	18.757
2006	10.303
2007	2.634
2008	7.468
2009	4.357
2010	52.259
2011	25.425
2012	12.472
2013	-1.539
2014	12.120
2015	6.408
2016	12.493
2017	21.194
2018	5.874
2019	0.249
2020	0.153
2021	7.754
2022	-7.383
2023	-10.434
2024	8.158
2025	6.815
2026	2.279
2027	3.041
2028	5.618
2029	5.851