{"year":1945,"thickness":51.8}
{"year":1945,"thickness":54.6}
{"year":1946,"thickness":53.2}
{"year":1946,"thickness":54.2}
{"year":1947,"thickness":53}
{"year":1947,"thickness":53}
{"year":1948,"thickness":53.6}
{"year":1948,"thickness":52.2}
{"year":1949,"thickness":53.2}
{"year":1949,"thickness":51.6}
{"year":1950,"thickness":53.4}
{"year":1950,"thickness":51}
{"year":1951,"thickness":53.4}
{"year":1951,"thickness":54}
{"year":1952,"thickness":53.4}
{"year":1952,"thickness":54.6}
{"year":1953,"thickness":50.6}
{"year":1953,"thickness":54.8}
{"year":1954,"thickness":52.2}
{"year":1954,"thickness":54.6}
{"year":1955,"thickness":52.6}
{"year":1955,"thickness":54.2}
{"year":1956,"thickness":54}
{"year":1956,"thickness":53.6}
{"year":1957,"thickness":53.6}
{"year":1957,"thickness":55}
{"year":1958,"thickness":53.2}
{"year":1958,"thickness":53.2}
{"year":1959,"thickness":56.8}
{"year":1959,"thickness":57.2}
{"year":1960,"thickness":57}
{"year":1960,"thickness":55.2}
{"year":1961,"thickness":56.6}
{"year":1961,"thickness":57}
{"year":1962,"thickness":54.6}
{"year":1962,"thickness":56}
{"year":1963,"thickness":58}
{"year":1963,"thickness":56.2}
{"year":1964,"thickness":55}
{"year":1964,"thickness":56}
{"year":1965,"thickness":56.6}
{"year":1965,"thickness":58.2}
{"year":1966,"thickness":57.2}
{"year":1966,"thickness":56}
{"year":1967,"thickness":57.6}
{"year":1967,"thickness":55.8}
{"year":1968,"thickness":57.2}
{"year":1968,"thickness":56}
{"year":1969,"thickness":58}
{"year":1969,"thickness":56}
{"year":1970,"thickness":57.2}
{"year":1970,"thickness":55.6}
{"year":1971,"thickness":58}
{"year":1971,"thickness":55.8}
{"year":1972,"thickness":57}
{"year":1972,"thickness":57}
{"year":1973,"thickness":59}
{"year":1973,"thickness":57.6}
{"year":1974,"thickness":59}
{"year":1974,"thickness":54}
{"year":1975,"thickness":54}
{"year":1975,"thickness":54.2}
{"year":1976,"thickness":53.2}
{"year":1976,"thickness":53.2}
{"year":1977,"thickness":54}
{"year":1977,"thickness":53.2}
{"year":1978,"thickness":53}
{"year":1978,"thickness":53.6}
{"year":1979,"thickness":54}
{"year":1979,"thickness":53}
{"year":1980,"thickness":53.6}
{"year":1980,"thickness":53}
{"year":1981,"thickness":54.8}
{"year":1981,"thickness":54}
{"year":1982,"thickness":54.4}
{"year":1982,"thickness":54.6}
{"year":1983,"thickness":52.8}
{"year":1983,"thickness":52.6}
{"year":1984,"thickness":55.2}
{"year":1984,"thickness":54}
{"year":1985,"thickness":55.6}
{"year":1985,"thickness":56}
{"year":1986,"thickness":55}
{"year":1986,"thickness":53.2}
{"year":1987,"thickness":55}
{"year":1987,"thickness":54}
{"year":1988,"thickness":54}
{"year":1988,"thickness":55.6}
{"year":1989,"thickness":56.2}
{"year":1989,"thickness":54}