Year	Percent change (Units)
1980	-3.497
1981	5.797
1982	8.150
1983	7.093
1984	8.397
1985	5.619
1986	3.357
1987	2.549
1988	5.100
1989	7.800
1990	5.047
1991	5.809
1992	8.700
1993	8.078
1994	8.834
1995	9.540
1996	9.340
1997	8.152
1998	5.765
1999	4.774
2000	6.787
2001	6.895
2002	7.080
2003	7.341
2004	7.789
2005	7.547
2006	6.978
2007	7.129
2008	5.662
2009	5.398
2010	6.423
2011	6.413
2012	5.505
2013	5.554
2014	6.422
2015	6.987
2016	6.690
2017	6.940
2018	7.465
2019	7.359
2020	2.867
2021	2.552
2022	8.124
2023	5.046
2024	5.815
2025	6.500
2026	6.500
2027	6.500
2028	6.500
2029	6.500