Monthly Millions Of Hours
1921-07-01 10.9800
1921-08-01 10.9100
1921-09-01 10.5400
1921-10-01 10.4200
1921-11-01 10.0900
1921-12-01 10.5500
1922-01-01 10.3400
1922-02-01 9.33000
1922-03-01 10.2600
1922-04-01 9.85000
1922-05-01 10.2200
1922-06-01 10.3500
1922-07-01 10.6900
1922-08-01 10.6500
1922-09-01 10.2200
1922-10-01 10.1700
1922-11-01 10.1400
1922-12-01 10.7700
1923-01-01 10.6900
1923-02-01 9.68000
1923-03-01 10.6800
1923-04-01 10.1600
1923-05-01 10.6600
1923-06-01 10.5600
1923-07-01 11.1100
1923-08-01 11.1600
1923-09-01 10.6600
1923-10-01 10.7300
1923-11-01 10.2700
1923-12-01 10.7600
1924-01-01 10.8200
1924-02-01 10.0000
1924-03-01 10.5100
1924-04-01 10.2600
1924-05-01 10.5900
1924-06-01 10.3700
1924-07-01 10.9100
1924-08-01 10.8900
1924-09-01 10.3700
1924-10-01 10.3600
1924-11-01 9.92000
1924-12-01 10.8500
1925-01-01 10.6800
1925-02-01 9.53000
1925-03-01 10.3300
1925-04-01 10.0900
1925-05-01 10.3500
1925-06-01 10.2400
1925-07-01 10.7900
1925-08-01 10.7300
1925-09-01 10.3100
1925-10-01 10.3700
1925-11-01 9.94000
1925-12-01 10.6400
1926-01-01 10.4100
1926-02-01 9.44000
1926-03-01 10.3000
1926-04-01 9.99000
1926-05-01 10.2200
1926-06-01 10.1400
1926-07-01 10.6600
1926-08-01 10.5400
1926-09-01 10.2700
1926-10-01 10.2000
1926-11-01 9.88000
1926-12-01 10.6700
1927-01-01 10.3800
1927-02-01 9.27000
1927-03-01 10.1600
1927-04-01 9.85000
1927-05-01 10.0400
1927-06-01 9.90000
1927-07-01 10.4700
1927-08-01 10.4300
1927-09-01 9.93000
1927-10-01 9.80000
1927-11-01 9.44000
1927-12-01 10.1500
1928-01-01 9.93000
1928-02-01 9.16000
1928-03-01 9.72000
1928-04-01 9.32000
1928-05-01 9.63000
1928-06-01 9.58000
1928-07-01 10.1200
1928-08-01 9.98000
1928-09-01 9.47000
1928-10-01 9.50000
1928-11-01 9.06000
1928-12-01 9.67000
1929-01-01 9.70000
1929-02-01 8.72000
1929-03-01 9.56000
1929-04-01 9.17000
1929-05-01 9.52000
1929-06-01 9.49000
1929-07-01 9.94000
1929-08-01 9.96000
1929-09-01 9.44000
1929-10-01 9.50000
1929-11-01 9.10000
1929-12-01 9.84000
1930-01-01 9.65000
1930-02-01 8.25000
1930-03-01 9.29000
1930-04-01 8.92000
1930-05-01 9.11000
1930-06-01 8.85000
1930-07-01 9.22000
1930-08-01 9.14000
1930-09-01 8.50000
1930-10-01 8.50000
1930-11-01 8.09000
1930-12-01 8.58000
1931-01-01 8.35000
1931-02-01 7.45000
1931-03-01 8.13000
1931-04-01 7.80000
1931-05-01 7.88000
1931-06-01 7.61000
1931-07-01 7.95000
1931-08-01 7.81000
1931-09-01 7.42000
1931-10-01 7.31000
1931-11-01 6.92000
1931-12-01 7.33000
1932-01-01 7.06000
1932-02-01 6.53000
1932-03-01 6.87000
1932-04-01 6.51000
1932-05-01 6.61000
1932-06-01 6.35000
1932-07-01 6.50000
1932-08-01 6.36000
1932-09-01 6.05000
1932-10-01 5.98000
1932-11-01 5.80000
1932-12-01 6.25000
1933-01-01 5.93000
1933-02-01 5.40000
1933-03-01 5.80000
1933-04-01 5.49000
1933-05-01 5.67000
1933-06-01 5.74000
1933-07-01 5.89000
1933-08-01 5.96000
1933-09-01 5.82000
1933-10-01 5.88000
1933-11-01 5.50000
1933-12-01 5.96000
1934-01-01 5.78000
1934-02-01 5.31000
1934-03-01 5.82000
1934-04-01 5.57000
1934-05-01 5.80000
1934-06-01 5.71000
1934-07-01 5.97000
1934-08-01 6.00000
1934-09-01 5.68000
1934-10-01 5.78000
1934-11-01 5.42000
1934-12-01 6.02000
1935-01-01 5.90000
1935-02-01 5.26000
1935-03-01 5.72000
1935-04-01 5.61000
1935-05-01 5.77000
1935-06-01 5.66000
1935-07-01 5.92000
1935-08-01 5.97000
1935-09-01 5.65000
1935-10-01 5.72000
1935-11-01 5.50000
1935-12-01 6.18000
1936-01-01 6.17000
1936-02-01 5.91000
1936-03-01 6.01000
1936-04-01 5.79000
1936-05-01 5.90000
1936-06-01 5.82000
1936-07-01 6.28000
1936-08-01 6.22000
1936-09-01 6.04000
1936-10-01 6.19000
1936-11-01 5.89000
1936-12-01 6.70000
1937-01-01 6.54000
1937-02-01 5.82000
1937-03-01 6.32000
1937-04-01 6.11000
1937-05-01 6.19000
1937-06-01 6.13000
1937-07-01 6.54000
1937-08-01 6.44000
1937-09-01 6.20000
1937-10-01 6.16000
1937-11-01 5.86000
1937-12-01 6.50000
1938-01-01 6.21000
1938-02-01 5.46000
1938-03-01 5.96000
1938-04-01 5.70000
1938-05-01 5.70000
1938-06-01 5.71000
1938-07-01 6.01000
1938-08-01 5.90000
1938-09-01 5.76000
1938-10-01 5.66000
1938-11-01 5.47000
1938-12-01 6.12000
1939-01-01 5.81000
1939-02-01 5.23000
1939-03-01 5.72000
1939-04-01 5.50000
1939-05-01 5.63000
1939-06-01 5.65000
1939-07-01 6.01000
1939-08-01 5.98000
1939-09-01 5.71000
1939-10-01 5.65000
1939-11-01 5.38000
1939-12-01 6.07000
1940-01-01 6.00000
1940-02-01 5.34000
1940-03-01 5.67000
1940-04-01 5.44000
1940-05-01 5.50000
1940-06-01 5.48000