Monthly Millions Of Hours
1921-07-01 4.07000
1921-08-01 4.67000
1921-09-01 4.98000
1921-10-01 6.11000
1921-11-01 5.05000
1921-12-01 4.03000
1922-01-01 4.34000
1922-02-01 4.56000
1922-03-01 5.08000
1922-04-01 3.77000
1922-05-01 4.26000
1922-06-01 4.64000
1922-07-01 5.22000
1922-08-01 7.00000
1922-09-01 8.40000
1922-10-01 9.54000
1922-11-01 9.52000
1922-12-01 9.54000
1923-01-01 9.34000
1923-02-01 8.74000
1923-03-01 9.22000
1923-04-01 7.68000
1923-05-01 7.40000
1923-06-01 7.05000
1923-07-01 6.89000
1923-08-01 7.58000
1923-09-01 7.37000
1923-10-01 8.40000
1923-11-01 7.18000
1923-12-01 5.79000
1924-01-01 6.91000
1924-02-01 6.79000
1924-03-01 6.02000
1924-04-01 4.87000
1924-05-01 4.81000
1924-06-01 4.55000
1924-07-01 4.77000
1924-08-01 5.29000
1924-09-01 6.02000
1924-10-01 6.68000
1924-11-01 5.80000
1924-12-01 6.02000
1925-01-01 6.23000
1925-02-01 5.24000
1925-03-01 4.70000
1925-04-01 4.32000
1925-05-01 4.41000
1925-06-01 4.57000
1925-07-01 4.94000
1925-08-01 5.56000
1925-09-01 5.90000
1925-10-01 6.86000
1925-11-01 6.28000
1925-12-01 5.93000
1926-01-01 5.67000
1926-02-01 5.56000
1926-03-01 5.54000
1926-04-01 4.70000
1926-05-01 4.65000
1926-06-01 4.74000
1926-07-01 5.11000
1926-08-01 5.60000
1926-09-01 6.24000
1926-10-01 6.82000
1926-11-01 6.50000
1926-12-01 6.27000
1927-01-01 5.48000
1927-02-01 4.64000
1927-03-01 4.84000
1927-04-01 4.48000
1927-05-01 4.61000
1927-06-01 4.47000
1927-07-01 4.37000
1927-08-01 5.13000
1927-09-01 5.43000
1927-10-01 5.50000
1927-11-01 4.43000
1927-12-01 4.16000
1928-01-01 3.90000
1928-02-01 3.58000
1928-03-01 3.89000
1928-04-01 3.55000
1928-05-01 3.76000
1928-06-01 3.65000
1928-07-01 3.84000
1928-08-01 4.53000
1928-09-01 4.71000
1928-10-01 5.38000
1928-11-01 4.28000
1928-12-01 3.51000
1929-01-01 4.00000
1929-02-01 4.05000
1929-03-01 3.84000
1929-04-01 3.62000
1929-05-01 3.84000
1929-06-01 3.75000
1929-07-01 4.02000
1929-08-01 4.44000
1929-09-01 4.55000
1929-10-01 5.13000
1929-11-01 3.82000
1929-12-01 3.46000
1930-01-01 3.59000
1930-02-01 2.84000
1930-03-01 2.82000
1930-04-01 2.80000
1930-05-01 2.85000
1930-06-01 2.66000
1930-07-01 2.82000
1930-08-01 2.94000
1930-09-01 2.99000
1930-10-01 3.28000
1930-11-01 2.35000
1930-12-01 1.96000
1931-01-01 1.91000
1931-02-01 1.64000
1931-03-01 1.90000
1931-04-01 1.90000
1931-05-01 1.83000
1931-06-01 1.80000
1931-07-01 1.91000
1931-08-01 1.91000
1931-09-01 1.88000
1931-10-01 2.06000
1931-11-01 1.55000
1931-12-01 1.35000
1932-01-01 1.29000
1932-02-01 1.26000
1932-03-01 1.39000
1932-04-01 1.11000
1932-05-01 1.01000
1932-06-01 1.01000
1932-07-01 1.02000
1932-08-01 1.17000
1932-09-01 1.43000
1932-10-01 1.67000
1932-11-01 1.22000
1932-12-01 1.18000
1933-01-01 0.950000
1933-02-01 1.10000
1933-03-01 0.950000
1933-04-01 0.980000
1933-05-01 1.14000
1933-06-01 1.29000
1933-07-01 1.45000
1933-08-01 1.48000
1933-09-01 1.53000
1933-10-01 1.51000
1933-11-01 1.26000
1933-12-01 1.19000
1934-01-01 1.30000
1934-02-01 1.43000
1934-03-01 1.50000
1934-04-01 1.10000
1934-05-01 1.20000
1934-06-01 1.24000
1934-07-01 1.26000
1934-08-01 1.39000
1934-09-01 1.49000
1934-10-01 1.58000
1934-11-01 1.25000
1934-12-01 1.23000
1935-01-01 1.53000
1935-02-01 1.29000
1935-03-01 1.27000
1935-04-01 1.13000
1935-05-01 1.12000
1935-06-01 1.27000
1935-07-01 1.27000
1935-08-01 1.46000
1935-09-01 1.60000
1935-10-01 1.84000
1935-11-01 1.43000
1935-12-01 1.42000
1936-01-01 1.81000
1936-02-01 2.52000
1936-03-01 1.89000
1936-04-01 1.64000
1936-05-01 1.49000
1936-06-01 1.51000
1936-07-01 1.72000
1936-08-01 1.78000
1936-09-01 1.94000
1936-10-01 2.26000
1936-11-01 1.89000
1936-12-01 1.90000
1937-01-01 1.99000
1937-02-01 2.01000
1937-03-01 1.91000
1937-04-01 1.63000
1937-05-01 1.60000
1937-06-01 1.66000
1937-07-01 1.77000
1937-08-01 1.81000
1937-09-01 1.97000
1937-10-01 2.03000
1937-11-01 1.47000
1937-12-01 1.42000
1938-01-01 1.22000
1938-02-01 1.05000
1938-03-01 1.21000
1938-04-01 1.04000
1938-05-01 1.02000
1938-06-01 1.10000
1938-07-01 1.22000
1938-08-01 1.38000
1938-09-01 1.62000
1938-10-01 1.80000
1938-11-01 1.42000
1938-12-01 1.29000
1939-01-01 1.18000
1939-02-01 1.16000
1939-03-01 1.22000
1939-04-01 1.07000
1939-05-01 1.16000
1939-06-01 1.24000
1939-07-01 1.29000
1939-08-01 1.47000
1939-09-01 1.84000
1939-10-01 2.11000
1939-11-01 1.66000
1939-12-01 1.39000
1940-01-01 1.74000
1940-02-01 1.38000
1940-03-01 1.28000
1940-04-01 1.25000
1940-05-01 1.33000
1940-06-01 1.38000