Year	Percent change (Units)
1980	2.000
1981	4.200
1982	17.695
1983	28.198
1984	30.044
1985	30.785
1986	40.491
1987	164.115
1988	58.507
1989	42.076
1990	43.723
1991	33.258
1992	45.076
1993	42.255
1994	63.123
1995	47.668
1996	48.491
1997	7.360
1998	1.487
1999	2.874
2000	12.713
2001	9.061
2002	16.769
2003	13.455
2004	12.634
2005	6.428
2006	13.245
2007	10.404
2008	14.505
2009	3.785
2010	12.428
2011	11.165
2012	2.602
2013	4.261
2014	2.561
2015	3.552
2016	17.417
2017	15.113
2018	3.911
2019	2.781
2020	3.142
2021	5.688
2022	9.770
2023	6.140
2024	4.439
2025	5.538
2026	5.147
2027	5.500
2028	5.500
2029	5.500