Year	Percent change (Units)
1980	11.346
1981	12.654
1982	7.736
1983	12.558
1984	6.518
1985	6.251
1986	8.890
1987	9.058
1988	7.214
1989	4.570
1990	11.198
1991	13.481
1992	9.862
1993	7.283
1994	10.272
1995	9.960
1996	9.433
1997	6.845
1998	13.126
1999	3.425
2000	3.817
2001	4.442
2002	4.997
2003	4.096
2004	3.997
2005	3.679
2006	6.736
2007	5.919
2008	9.212
2009	10.607
2010	9.368
2011	8.112
2012	10.049
2013	9.383
2014	5.833
2015	4.908
2016	4.525
2017	3.587
2018	3.414
2019	4.769
2020	6.165
2021	5.506
2022	6.653
2023	5.375
2024	4.563
2025	4.167
2026	4.092
2027	4.000
2028	4.000
2029	4.000