Year	Percent change (Units)
1981	58.137
1982	-26.461
1983	43.063
1984	-18.051
1985	17.511
1986	58.201
1987	35.182
1988	11.847
1989	-21.978
1990	12.762
1991	-3.297
1992	60.420
1993	-0.554
1994	13.437
1995	106.004
1996	85.469
1997	151.130
1998	38.659
1999	20.856
2000	-11.998
2001	40.963
2002	11.790
2003	3.067
2004	59.081
2005	48.573
2006	8.538
2007	1.654
2008	20.699
2009	-16.274
2010	0.378
2011	-7.353
2012	8.108
2013	-3.148
2014	6.416
2015	4.140
2016	-11.344
2017	-16.271
2018	-7.054
2019	-20.158
2020	23.494
2021	15.034
2022	-17.383
2023	-13.581
2024	7.454
2025	-14.436
2026	-13.865
2027	-4.289
2028	-8.272
2029	-4.301