Year	Percent change (Units)
1981	-15.188
1982	-29.006
1983	-23.974
1984	-19.878
1985	4.531
1986	24.041
1987	18.534
1988	-28.907
1989	28.052
1990	13.419
1991	-15.368
1992	-2.112
1993	44.102
1994	-1.590
1995	-18.941
1996	34.577
1997	-61.377
1998	16.371
1999	-4.699
2000	53.149
2001	27.674
2002	51.058
2003	6.452
2004	-21.056
2005	18.682
2006	-5.625
2007	-6.522
2008	7.255
2009	48.202
2010	35.156
2011	117.264
2012	-6.787
2013	-17.789
2014	6.737
2015	-5.303
2016	-22.827
2017	19.398
2018	-4.027
2019	16.367
2020	-5.073
2021	17.064
2022	-6.481
2023	2.709
2024	9.647
2025	-0.984
2026	1.453
2027	3.356
2028	3.814
2029	3.905