Year	Percent change (Units)
1981	14.410
1982	11.538
1983	10.626
1984	18.650
1985	18.211
1986	8.895
1987	16.253
1988	17.849
1989	8.642
1990	10.985
1991	9.556
1992	8.567
1993	13.199
1994	13.815
1995	10.134
1996	5.763
1997	7.756
1998	4.904
1999	9.098
2000	6.427
2001	10.784
2002	11.486
2003	4.633
2004	3.227
2005	7.600
2006	4.799
2007	9.808
2008	12.904
2009	4.501
2010	4.500
2011	7.763
2012	8.265
2013	4.419
2014	6.169
2015	4.910
2016	8.682
2017	4.706
2018	5.220
2019	2.003
2020	4.589
2021	3.454
2022	5.590
2023	4.311
2024	3.115
2025	3.010
2026	2.982
2027	3.035
2028	3.035
2029	3.035