Year	Percent change (Units)
1980	7.692
1981	14.935
1982	13.653
1983	11.102
1984	9.993
1985	10.441
1986	10.313
1987	10.518
1988	10.222
1989	9.182
1990	9.665
1991	9.348
1992	5.862
1993	3.296
1994	4.588
1995	8.857
1996	6.838
1997	2.661
1998	6.657
1999	8.904
2000	3.623
2001	1.812
2002	2.407
2003	3.881
2004	8.139
2005	6.486
2006	7.163
2007	7.205
2008	9.937
2009	6.655
2010	7.316
2011	8.787
2012	8.889
2013	6.777
2014	7.349
2015	6.405
2016	5.916
2017	5.440
2018	5.783
2019	5.475
2020	5.648
2021	5.558
2022	6.150
2023	9.016
2024	9.300
2025	6.100
2026	5.730
2027	5.500
2028	5.500
2029	5.500