Month	Millions Of Hours
1926-01-01	2.87000
1926-02-01	2.62000
1926-03-01	2.96000
1926-04-01	3.11000
1926-05-01	3.42000
1926-06-01	3.32000
1926-07-01	3.37000
1926-08-01	3.26000
1926-09-01	3.24000
1926-10-01	3.30000
1926-11-01	2.98000
1926-12-01	2.97000
1927-01-01	2.96000
1927-02-01	2.80000
1927-03-01	3.27000
1927-04-01	3.25000
1927-05-01	3.51000
1927-06-01	3.38000
1927-07-01	3.51000
1927-08-01	3.42000
1927-09-01	3.41000
1927-10-01	3.69000
1927-11-01	3.33000
1927-12-01	3.18000
1928-01-01	3.23000
1928-02-01	3.18000
1928-03-01	3.48000
1928-04-01	3.48000
1928-05-01	3.84000
1928-06-01	3.68000
1928-07-01	3.84000
1928-08-01	3.80000
1928-09-01	3.67000
1928-10-01	3.91000
1928-11-01	3.58000
1928-12-01	3.62000
1929-01-01	3.48000
1929-02-01	3.21000
1929-03-01	3.73000
1929-04-01	3.84000
1929-05-01	4.07000
1929-06-01	4.05000
1929-07-01	4.27000
1929-08-01	4.11000
1929-09-01	4.03000
1929-10-01	4.27000
1929-11-01	3.91000
1929-12-01	3.81000
1930-01-01	3.61000
1930-02-01	3.56000
1930-03-01	3.99000
1930-04-01	4.06000
1930-05-01	4.20000
1930-06-01	3.94000
1930-07-01	4.02000
1930-08-01	3.91000
1930-09-01	3.81000
1930-10-01	4.10000
1930-11-01	3.80000
1930-12-01	3.82000
1931-01-01	3.70000
1931-02-01	3.47000
1931-03-01	3.87000
1931-04-01	3.87000
1931-05-01	4.16000
1931-06-01	3.97000
1931-07-01	4.15000
1931-08-01	3.83000
1931-09-01	3.63000
1931-10-01	3.81000
1931-11-01	3.59000
1931-12-01	3.54000
1932-01-01	3.44000
1932-02-01	3.28000
1932-03-01	3.50000
1932-04-01	3.51000
1932-05-01	3.64000
1932-06-01	3.40000
1932-07-01	3.46000
1932-08-01	3.25000
1932-09-01	3.24000
1932-10-01	3.62000
1932-11-01	3.38000
1932-12-01	3.37000
1933-01-01	3.35000
1933-02-01	2.98000
1933-03-01	3.29000
1933-04-01	3.27000
1933-05-01	3.50000
1933-06-01	3.52000
1933-07-01	3.73000
1933-08-01	3.69000
1933-09-01	3.58000
1933-10-01	3.81000
1933-11-01	3.62000
1933-12-01	3.55000
1934-01-01	3.61000
1934-02-01	3.29000
1934-03-01	3.86000
1934-04-01	3.88000
1934-05-01	4.08000
1934-06-01	4.01000
1934-07-01	4.06000
1934-08-01	4.02000
1934-09-01	3.83000
1934-10-01	4.01000
1934-11-01	3.71000
1934-12-01	3.71000
1935-01-01	3.75000
1935-02-01	3.52000
1935-03-01	4.09000
1935-04-01	4.01000
1935-05-01	4.17000
1935-06-01	4.01000
1935-07-01	4.02000
1935-08-01	3.96000
1935-09-01	3.95000
1935-10-01	4.34000
1935-11-01	4.08000
1935-12-01	4.07000
1936-01-01	4.03000
1936-02-01	3.66000
1936-03-01	4.20000
1936-04-01	4.31000
1936-05-01	4.58000
1936-06-01	4.46000
1936-07-01	4.60000
1936-08-01	4.52000
1936-09-01	4.44000
1936-10-01	4.83000
1936-11-01	4.69000
1936-12-01	4.86000
1937-01-01	4.68000
1937-02-01	4.29000
1937-03-01	5.03000
1937-04-01	4.91000
1937-05-01	5.18000
1937-06-01	5.04000
1937-07-01	5.02000
1937-08-01	4.82000
1937-09-01	4.72000
1937-10-01	5.13000
1937-11-01	4.55000
1937-12-01	4.42000
1938-01-01	4.20000
1938-02-01	3.90000
1938-03-01	4.30000
1938-04-01	4.10000
1938-05-01	4.21000
1938-06-01	4.09000
1938-07-01	4.21000
1938-08-01	4.24000
1938-09-01	4.16000
1938-10-01	4.58000
1938-11-01	4.32000
1938-12-01	4.50000
1939-01-01	4.46000
1939-02-01	4.88000
1939-03-01	4.67000
1939-04-01	4.49000
1939-05-01	4.65000
1939-06-01	4.63000
1939-07-01	4.69000
1939-08-01	4.63000
1939-09-01	4.70000
1939-10-01	5.09000
1939-11-01	4.88000
1939-12-01	4.80000
1940-01-01	4.66000
1940-02-01	4.52000
1940-03-01	4.84000
1940-04-01	4.77000
1940-05-01	5.04000
1940-06-01	4.86000