Year	Percent change (Units)
1981	10.986
1982	8.013
1983	5.261
1984	24.966
1985	-5.535
1986	4.432
1987	4.985
1988	5.359
1989	12.002
1990	10.732
1991	8.338
1992	3.522
1993	15.532
1994	13.157
1995	19.169
1996	37.384
1997	26.604
1998	-1.210
1999	21.027
2000	14.093
2001	3.685
2002	3.280
2003	10.854
2004	12.067
2005	1.075
2006	9.001
2007	14.694
2008	25.674
2009	4.629
2010	4.082
2011	14.855
2012	11.841
2013	9.017
2014	3.745
2015	7.132
2016	9.497
2017	10.499
2018	-5.877
2019	5.142
2020	7.511
2021	10.073
2022	26.494
2023	20.128
2024	22.915
2025	17.628
2026	17.014
2027	14.032
2028	23.329
2029	8.785