year	activity
1916	57.1
1917	103.9
1918	80.6
1919	63.6
1920	37.6
1921	26.1
1922	14.2
1923	5.8
1924	16.7
1925	44.3
1926	63.9
1927	69
1928	77.8
1929	64.9
1930	35.7
1931	21.2
1932	11.1
1933	5.7
1934	8.7
1935	36.1
1936	79.7
1937	114.4
1938	109.6
1939	88.8
1940	67.8
1941	47.5
1942	30.6
1943	16.3
1944	9.6
1945	33.2
1946	92.6
1947	151.6
1948	136.3
1949	134.7
1950	83.9
1951	69.4
1952	31.5
1953	13.9
1954	4.4
1955	38