Year	Percent change (Units)
1980	6.736
1981	6.007
1982	3.475
1983	7.289
1984	3.820
1985	5.254
1986	4.777
1987	3.965
1988	9.628
1989	5.947
1990	5.534
1991	1.057
1992	5.483
1993	4.751
1994	6.659
1995	7.574
1996	7.550
1997	4.050
1998	6.184
1999	8.846
2000	3.841
2001	4.824
2002	3.804
2003	7.860
2004	7.923
2005	7.923
2006	8.061
2007	7.661
2008	3.087
2009	7.862
2010	8.498
2011	5.241
2012	5.456
2013	6.386
2014	7.410
2015	7.996
2016	8.256
2017	6.795
2018	6.454
2019	3.871
2020	-5.778
2021	9.690
2022	6.987
2023	7.827
2024	6.808
2025	6.458
2026	6.467
2027	6.477
2028	6.486
2029	6.495