Year	Percent change (Units)
1980	63.475
1981	34.046
1982	18.991
1983	49.198
1984	55.305
1985	72.222
1986	76.380
1987	63.567
1988	62.192
1989	80.447
1990	112.526
1991	101.972
1992	68.456
1993	54.081
1994	44.736
1995	42.248
1996	28.342
1997	19.819
1998	10.808
1999	5.660
2000	4.775
2001	4.357
2002	13.968
2003	19.379
2004	9.169
2005	4.699
2006	6.386
2007	8.115
2008	7.878
2009	7.068
2010	6.694
2011	8.092
2012	8.099
2013	8.577
2014	8.878
2015	8.660
2016	9.640
2017	6.222
2018	7.606
2019	7.883
2020	9.754
2021	7.750
2022	9.106
2023	5.868
2024	5.765
2025	5.509
2026	5.228
2027	4.879
2028	4.590
2029	4.567