Year	Percent change (Units)
1981	9.521
1982	23.339
1983	29.701
1984	29.790
1985	33.893
1986	41.397
1987	185.325
1988	51.327
1989	28.380
1990	47.099
1991	35.214
1992	54.500
1993	43.638
1994	56.558
1995	56.537
1996	19.343
1997	6.197
1998	-0.956
1999	6.216
2000	11.438
2001	21.935
2002	9.119
2003	13.815
2004	9.067
2005	11.148
2006	9.374
2007	12.545
2008	11.831
2009	2.242
2010	17.446
2011	6.141
2012	2.020
2013	3.538
2014	1.925
2015	10.554
2016	21.152
2017	5.648
2018	3.524
2019	3.503
2020	3.520
2021	6.740
2022	10.288
2023	4.251
2024	4.726
2025	5.519
2026	5.500
2027	5.500
2028	5.500
2029	5.500