Month	Millions Of Hours
1921-07-01	10.1800
1921-08-01	9.15000
1921-09-01	8.95000
1921-10-01	10.2300
1921-11-01	8.76000
1921-12-01	7.50000
1922-01-01	8.38000
1922-02-01	8.48000
1922-03-01	8.98000
1922-04-01	7.20000
1922-05-01	7.91000
1922-06-01	8.50000
1922-07-01	15.0000
1922-08-01	25.1200
1922-09-01	30.7400
1922-10-01	28.6700
1922-11-01	25.1700
1922-12-01	24.5400
1923-01-01	22.8600
1923-02-01	20.8700
1923-03-01	20.3100
1923-04-01	17.2100
1923-05-01	17.4700
1923-06-01	16.4500
1923-07-01	16.5300
1923-08-01	16.3600
1923-09-01	16.3800
1923-10-01	17.0500
1923-11-01	14.9300
1923-12-01	12.6300
1924-01-01	14.4000
1924-02-01	14.8300
1924-03-01	12.6700
1924-04-01	10.2300
1924-05-01	10.2300
1924-06-01	9.74000
1924-07-01	10.1200
1924-08-01	10.8300
1924-09-01	12.0700
1924-10-01	12.6700
1924-11-01	12.0900
1924-12-01	13.0400
1925-01-01	14.4800
1925-02-01	11.7400
1925-03-01	10.1700
1925-04-01	9.06000
1925-05-01	9.97000
1925-06-01	9.74000
1925-07-01	10.8600
1925-08-01	11.6200
1925-09-01	12.5700
1925-10-01	13.9100
1925-11-01	13.7600
1925-12-01	12.9600
1926-01-01	13.0400
1926-02-01	13.8900
1926-03-01	12.0500
1926-04-01	10.3300
1926-05-01	11.0600
1926-06-01	10.4600
1926-07-01	11.7500
1926-08-01	12.3600
1926-09-01	14.2600
1926-10-01	14.7000
1926-11-01	14.2800
1926-12-01	14.4700
1927-01-01	13.4600
1927-02-01	11.8400
1927-03-01	10.4600
1927-04-01	10.4000
1927-05-01	11.5500
1927-06-01	10.1300
1927-07-01	10.7800
1927-08-01	10.9300
1927-09-01	11.8800
1927-10-01	12.0000
1927-11-01	10.6200
1927-12-01	10.5600
1928-01-01	10.5700
1928-02-01	9.09000
1928-03-01	9.04000
1928-04-01	8.41000
1928-05-01	8.95000
1928-06-01	8.57000
1928-07-01	9.76000
1928-08-01	10.1200
1928-09-01	11.2000
1928-10-01	11.3800
1928-11-01	10.0900
1928-12-01	9.41000
1929-01-01	10.9300
1929-02-01	10.8300
1929-03-01	9.87000
1929-04-01	8.64000
1929-05-01	9.59000
1929-06-01	9.24000
1929-07-01	9.97000
1929-08-01	10.1800
1929-09-01	11.2000
1929-10-01	11.4300
1929-11-01	9.40000
1929-12-01	10.6800
1930-01-01	10.0100
1930-02-01	7.62000
1930-03-01	7.33000
1930-04-01	6.53000
1930-05-01	7.30000
1930-06-01	6.60000
1930-07-01	6.91000
1930-08-01	6.92000
1930-09-01	6.98000
1930-10-01	6.96000
1930-11-01	6.21000
1930-12-01	5.48000
1931-01-01	5.33000
1931-02-01	4.91000
1931-03-01	5.54000
1931-04-01	4.64000
1931-05-01	5.04000
1931-06-01	4.52000
1931-07-01	5.10000
1931-08-01	4.83000
1931-09-01	4.78000
1931-10-01	4.54000
1931-11-01	4.23000
1931-12-01	3.87000
1932-01-01	4.06000
1932-02-01	3.83000
1932-03-01	4.06000
1932-04-01	2.95000
1932-05-01	3.14000
1932-06-01	2.81000
1932-07-01	3.23000
1932-08-01	3.05000
1932-09-01	3.63000
1932-10-01	3.94000
1932-11-01	3.38000
1932-12-01	3.90000
1933-01-01	3.03000
1933-02-01	3.58000
1933-03-01	2.68000
1933-04-01	2.70000
1933-05-01	3.18000
1933-06-01	3.14000
1933-07-01	3.88000
1933-08-01	3.58000
1933-09-01	3.86000
1933-10-01	3.43000
1933-11-01	3.21000
1933-12-01	3.88000
1934-01-01	3.52000
1934-02-01	5.18000
1934-03-01	4.12000
1934-04-01	3.02000
1934-05-01	3.30000
1934-06-01	3.27000
1934-07-01	3.65000
1934-08-01	3.45000
1934-09-01	3.90000
1934-10-01	3.59000
1934-11-01	3.26000
1934-12-01	3.81000
1935-01-01	5.15000
1935-02-01	4.02000
1935-03-01	3.50000
1935-04-01	2.98000
1935-05-01	3.40000
1935-06-01	3.77000
1935-07-01	3.82000
1935-08-01	3.78000
1935-09-01	4.29000
1935-10-01	4.20000
1935-11-01	3.87000
1935-12-01	4.82000
1936-01-01	6.28000
1936-02-01	9.00000
1936-03-01	6.11000
1936-04-01	4.36000
1936-05-01	4.36000
1936-06-01	3.93000
1936-07-01	4.89000
1936-08-01	4.83000
1936-09-01	5.23000
1936-10-01	5.49000
1936-11-01	5.35000
1936-12-01	5.65000
1937-01-01	7.05000
1937-02-01	6.87000
1937-03-01	5.47000
1937-04-01	4.63000
1937-05-01	5.17000
1937-06-01	4.92000
1937-07-01	5.49000
1937-08-01	5.10000
1937-09-01	5.31000
1937-10-01	5.11000
1937-11-01	4.22000
1937-12-01	4.43000
1938-01-01	4.26000
1938-02-01	3.76000
1938-03-01	3.66000
1938-04-01	3.16000
1938-05-01	3.27000
1938-06-01	3.19000
1938-07-01	3.87000
1938-08-01	3.61000
1938-09-01	4.74000
1938-10-01	4.76000
1938-11-01	4.36000
1938-12-01	4.08000
1939-01-01	4.44000
1939-02-01	4.29000
1939-03-01	3.84000
1939-04-01	3.40000
1939-05-01	3.64000
1939-06-01	3.71000
1939-07-01	4.20000
1939-08-01	4.05000
1939-09-01	5.31000
1939-10-01	5.58000
1939-11-01	4.82000
1939-12-01	4.75000
1940-01-01	6.41000
1940-02-01	5.37000
1940-03-01	4.25000
1940-04-01	3.79000
1940-05-01	4.16000
1940-06-01	4.33000
1940-07-01	4.80000
1940-08-01	5.16000
1940-09-01	5.67000
1940-10-01	5.45000
1940-11-01	5.68000
1940-12-01	6.08000
1941-01-01	6.26000
1941-02-01	5.84000
1941-03-01	6.82000
1941-04-01	5.38000
1941-05-01	6.71000
1941-06-01	7.63000
1941-07-01	8.24000
1941-08-01	8.52000
1941-09-01	8.86000
1941-10-01	9.16000
1941-11-01	8.38000
1941-12-01	8.81000
1942-01-01	9.54000
1942-02-01	9.08000
1942-03-01	9.52000
1942-04-01	9.08000
1942-05-01	10.8300
1942-06-01	10.2700
1942-07-01	12.4300
1942-08-01	14.0400
1942-09-01	16.1600