Month	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