Year	Percent change (Units)
1980	25.932
1981	27.473
1982	23.276
1983	16.783
1984	18.563
1985	22.727
1986	20.576
1987	24.232
1988	28.297
1989	26.338
1990	32.373
1991	26.889
1992	25.227
1993	22.643
1994	22.602
1995	19.400
1996	21.544
1997	17.541
1998	16.462
1999	9.037
2000	8.511
2001	7.456
2002	6.832
2003	6.375
2004	5.452
2005	4.834
2006	4.459
2007	5.659
2008	7.621
2009	1.905
2010	3.084
2011	3.668
2012	2.442
2013	1.963
2014	3.700
2015	6.798
2016	5.745
2017	4.067
2018	3.149
2019	3.818
2020	1.647
2021	5.682
2022	13.187
2023	9.311
2024	5.334
2025	3.041
2026	2.952
2027	3.003
2028	3.003
2029	2.952