ID	Year	Yield
1	1957	23.2
2	1958	24.2
3	1959	23.5
4	1960	23.5
5	1961	25.1
6	1962	24.2
7	1963	24.4
8	1964	22.8
9	1965	24.5
10	1966	25.4
11	1967	24.5
12	1968	26.7
13	1969	27.4
14	1970	26.7
15	1971	27.5
16	1972	27.8
17	1973	27.8
18	1974	23.7
19	1975	28.9
20	1976	26.1
21	1977	30.6
22	1978	29.4
23	1979	32.1
24	1980	26.5
25	1981	30.1
26	1982	31.5
27	1983	26.2
28	1984	28.1
29	1985	34.1
30	1986	33.3
31	1987	33.9
32	1988	27
33	1989	32.3
34	1990	34.1
35	1991	34.2
36	1992	37.6
37	1993	32.6
38	1994	41.4
39	1995	35.3
40	1996	37.6
