Year	Measure
1800	1018
1820	1018
1913	1878
1950	3245
1960	5320
1961	5712
1962	6204
1963	5863
1964	6130
1965	6806
1966	7058
1967	7789
1968	8307
1969	8904
1970	9712
1971	9814
1972	9854
1973	9991
1974	11270
1975	10980
1976	11410
1977	11820
1978	12380
1979	13300
1980	13860
1981	13500
1982	12740
1983	12680
1984	13000
1985	13020
1986	13560
1987	13780
1988	14140
1989	14530
1990	13950
1991	13290
1992	12260
1993	12300
1994	12740
1995	13010
1996	13360
1997	13900
1998	14700
1999	14710
2000	14980
2001	14530
2002	14540
2003	14780
2004	15270
2005	15840
2006	16700
2007	16940
2008	16960
2009	16230
2010	16220
2011	16270
2012	16230
2013	16270
2014	16400
2015	16600
2016	16890
2017	17220
2018	17590