Year	Percent change (Units)
1981	-0.498
1982	4.200
1983	-3.400
1984	5.500
1985	4.300
1986	-1.000
1987	5.600
1988	1.958
1989	2.925
1990	4.580
1991	7.305
1992	3.095
1993	2.276
1994	2.963
1995	4.016
1996	3.747
1997	5.994
1998	-22.446
1999	16.815
2000	1.100
2001	4.786
2002	3.654
2003	-0.286
2004	1.172
2005	6.560
2006	2.667
2007	2.560
2008	4.525
2009	2.448
2010	5.605
2011	8.085
2012	-1.713
2013	3.256
2014	0.965
2015	6.134
2016	5.307
2017	4.789
2018	3.761
2019	4.500
2020	1.500
2021	6.400
2022	4.200
2023	4.200
2024	5.000
2025	5.000
2026	5.000
2027	5.000
2028	4.500
2029	4.500