amount of sickness data classified by sickness causes. The data for disabilities lasting one week or longer, brought down to the end of June. 1921, are presented herewith.2 As yet not enough morbidity material has been made available from benefit associations having waiting periods of two, three, or four days to permit the publication currently of cases of less than a week's duration. The present tabulation includes, therefore, only the more serious cases of sickness and nonindustrial accidents.

The restrictions of a large proportion of the reporting associations as to the age limits for eligibility to membership and the denial of sickness benefits for the venereal diseases and for certain other causes of disability prevent the statistics from being entirely comparable with those secured from other sources. On account of certain rules of a number of the reporting associations, especially the rule which refuses benefits for chronic diseases contracted prior to the date of joining the association, the rule forbidding payment for disabilities resulting from the violation of any civil law, or for the results of willful or gross negligence, it is believed that even for the illnesses lasting seven or eight days or longer the rates should be regarded as a minimum statement of the disabilities actually occurring.

The number of persons used as the divisor in calculating the frequency rates is the number of employees reported as holding membership in the various associations during each month. Only a small proportion of the membership is composed of women. While practically all of the reporting associations require a physician's certificate stating the ailment causing disability, errors in diagnosis undoubtedly have occurred. It is believed, however, that the diagnoses are sufficiently correct to afford a fairly good picture of serious morbidity among a certain group of working people. The disease classification used is the same as that in the International List of the Causes of Death, in accordance with the recommendation of the committee on industrial morbidity statistics of the American Public Health Association. Wherever related diseases are grouped in the accompanying tables not strictly in accordance with the International classification, a statement of the diseases included or excluded appears in the footnotes.

The frequency rates of the more prevalent diseases and important disease groups are presented in the first two tables according to the month in which disability began. The rates are placed on an annual basis; i. e., the rate for any month represents what the total sickness from any specified cause would have been for the whole year had the rate for that month been maintained throughout the year.

'In [inrioiij issues Ihe statistics tor the first half of 1920, for the first nine months of 1920, and for the lirrAu year 1920 have been discussed. These articles, entitled 'Sickness Frequency Amoni; Industrial fcmjil'.jTes," are as follows: (1) Reprint No. 62-1 from tho Public Health Reports of Dec. 3, 1920, pp. 2S97*B; <») Reprint No. 644 from the Public Health Reports of Mar. 4, 1921, pp. 429-431; (3) Reprint No. 671 from the Public Health Reports of July 1,1921, pp. 1497-1502.

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Table I.—Frequency of the principal disease groups by month of onset, January, 1920, to June, 1931, among a group of wage earners.1


»Annual number of cases per 1,000 members of certain sick-benefit associations reporting to the Public Health Service. Only cases lasting a week or longer are included. 1 Except the venereal diseases.

1 Including tuberculosis of the lungs and diseases of the pharynx. * Excluding diseases of the pharynx.

1 Excluding influenza, grippe, and tuberculosis of the lungs.

Seasonal Variation in Sickness Incident' '.

From the health point of view, the year ending June 30, 1921, may be considered a normal year, since the period was relatively free from major epidemics. Normal seasonal variation in sickness incidence, therefore, may be studied. From Figure 1 it is apparent that serious illness occurred about twice as often in the winter of 1920-21 as in the summer of 1920. It will also be noticed that the sickness rate for each of the months given in 1921 was somewhat higher than the rate for the corresponding month in 1920, with the exception of January and February, which were influenza months in 1920. The prevalence of respiratory diseases (influenza and grippe excepted) was about three times as great in February, 1921, as in June, 1921. The digestive diseases exhibit no tendency to be more prevalent in the hot-weather months than at any other time of the year.

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