Year	Percent change (Units)
1980	20.300
1981	9.600
1982	15.600
1983	16.735
1984	19.580
1985	11.404
1986	27.953
1987	25.110
1988	9.991
1989	16.653
1990	21.380
1991	20.709
1992	9.744
1993	14.953
1994	6.393
1995	9.725
1996	8.156
1997	4.761
1998	3.378
1999	2.877
2000	2.542
2001	2.500
2002	2.439
2003	4.167
2004	12.000
2005	4.592
2006	7.317
2007	8.636
2008	20.084
2009	9.756
2010	10.159
2011	11.816
2012	7.216
2013	9.856
2014	8.315
2015	11.313
2016	13.975
2017	29.777
2018	14.356
2019	9.359
2020	5.692
2021	4.893
2022	13.154
2023	35.727
2024	32.074
2025	15.291
2026	12.944
2027	9.038
2028	7.105
2029	5.204