Theoretically the correction ought to be extended so as to apply to visitors who do not die in public institutions. In practice, however, this cannot be effected, until a central “clearing house” is established. The exclusion of deaths of visitors from the district in which they occur is easy; their inclusion in the returns of the district from which they come is more difficult to secure. For the present, they should be included in the death-rate of the district in which they occur.
Death-rate according to Age and Sex.—To obtain a true conception of the death-rate in a community, it is necessary to state the number of deaths in each sex in proportion to the number living at different ages. The importance of this is shown by the following extract from the Registrar-General’s report for 1899.
England and Wales.—Deaths to 1,000 living at each of 12 groups of ages.
| ALL AGES. | AGED 0- | 5- | 10- | 15- | 20- | 25- | 35- | 45- | 55- | 65- | 75- | 85 AND UPWARDS. | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Males | 19·5 | 60·4 | 3·8 | 2·2 | 3·6 | 5·3 | 7·1 | 12·3 | 20·0 | 37·2 | 69·8 | 152·6 | 300·3 |
| Females | 17·3 | 50·7 | 3·9 | 2·3 | 3·3 | 4·3 | 6·1 | 10·0 | 15·4 | 29·8 | 61·5 | 142·6 | 272·0 |
Thus at ages over 5 and under 45 for males, and under 55 for females, the death-rate is lower than is the total death-rate for all ages. For females at all ages except from 5 to 15, the death-rate is lower than for males. From the above statement it will be clear that a considerable excess of women (as in a residential district with a large number of domestic servants) or a considerable excess of either sex at the ages of 15 to 45 (as in most large towns) in proportion to the number living at other ages, would produce a lower total or crude death-rate, which does not imply any truly more healthy condition than that of another district, which is less favourably constituted so far as the proportion of the sexes and the numbers living at different ages are concerned. By a means of correction now to be described this source of error can be eliminated. The method of obtaining the factor for correction can be best understood by an example. The annual death-rate of England and Wales in 1881-90 was 19.15, and the death-rate at each age-group is given in the following table:
| AGES. | MEAN ANNUAL DEATH-RATE IN ENGLAND AND WALES 1881-90, PER 1,000 LIVING AT EACH GROUP OF AGES. | POPULATIONOF HUDDERSFIELD IN 1891 | CALCULATED NUMBER OF DEATHSIN HUDDERSFIELD. | |||
|---|---|---|---|---|---|---|
| Under 5 | Males. 61.59 | Females. 51.95 | Males. 4,551 | Females. 4,785 | Males. 280 | Females. 249 |
| 5 | 5·35 | 5·27 | 4,691 | 5,081 | 25 | 27 |
| 10 | 2·96 | 3·11 | 5,113 | 5,165 | 15 | 16 |
| 15 | 4·33 | 4·42 | 4,905 | 5,549 | 21 | 25 |
| 20 | 5·73 | 5·54 | 4,541 | 5,461 | 26 | 30 |
| 25 | 7·78 | 7·41 | 7,466 | 8,834 | 58 | 65 |
| 35 | 12·41 | 10·61 | 5,576 | 6,265 | 69 | 66 |
| 45 | 19·36 | 15·09 | 3,944 | 4,649 | 76 | 70 |
| 55 | 34·69 | 28·45 | 2,393 | 3,017 | 83 | 86 |
| 65 | 70·39 | 60·36 | 1,128 | 1,590 | 79 | 96 |
| 75 and upwards | 162.62 | 147.98 | 250 | 466 | 41 | 69 |
| 44,558 | 50,862 | 773 | 799 | |||
| Totals | \————/ | \———/ | ||||
| 95,420 | 1,572 | |||||
The population of Huddersfield at each of the corresponding periods as given by the census of 1891, is also shown in this table, and in the last column the number of male and female deaths that would occur by applying the death-rates for England and Wales to the population of Huddersfield are shewn. The total number of deaths thus calculated is 1572 in a population of 95,420, and the total death-rate = 16·47 per 1000. This is the standard death-rate, i.e., the death-rate at all ages calculated on the hypothesis that the rates at each of 12 age-periods in Huddersfield were the same as in England and Wales during the ten years of the last intercensal period, viz. 19·15 in 1881-90.[13] But the standard death-rate of Huddersfield would have been 19·15 instead of 16·47, were it not for the fact that the distribution of age and sex in the Huddersfield population is more favourable than in the country as a whole. Hence it must be increased in the ratio of 19·15: 16·47, i.e., multiplied by the factor 19·15 ∕ 16·47 = 1·1627. When the crude or recorded death-rate for 1900 of 16·78 is multiplied by this factor we obtain the corrected death-rate of 16·78 × 1·1627 = 19·51 per 1000, which is the correct figure to compare with the death-rate of 18.31 for England and Wales in that year. If the death-rate of England and Wales be stated as 1000, then 1000 × 1951 ∕ 1831 = 1066, is the comparative mortality figure for Huddersfield. Similarly in the year 1900 the comparative mortality figure of London was 1093, of Croydon 831, of Norwich 919, while that of Liverpool was 1539, of Salford 1541. In all the towns except Plymouth and Norwich the corrected death-rate is higher than the crude or recorded death-rate. This implies that, in all except these two towns, the factor of correction is greater than unity.
This is a convenient point for briefly discussing the relationship between the birth-rate and death-rate. The opinion is commonly held that a high birth-rate is a direct cause of a high death-rate, owing to the great mortality amongst infants. The table on page [340] shows that the death-rate at ages under five is three times as high as at all ages together, and it is therefore natural to suppose that a high birth-rate by producing an excessive proportion of persons of tender years will cause a high general death-rate. This might be so, if the birth-rate were to remain high for only five years. But if the high birth-rate continued longer, the proportion of the total population at ages of low mortality would be increased, and the general death-rate would be lowered. We have already seen that in nearly all the great towns, in which the birth-rate is higher than in rural districts, the age distribution of the population is more favourable to a low death-rate than in rural districts; and their higher crude death-rate is made still higher than that of rural districts when the necessary factor of correction is applied.
The Infantile Mortality should be stated in terms of the infantile population. This is more accurately assumed to be equal to the number of births in the given year, than estimated from the number stated to be under one year of age at the last census. The number of deaths under one year of age per 1000 births was 163 for England and Wales in 1899, being lowest in the agricultural counties and highest in manufacturing counties. In the 33 great towns it averaged 172 in the year 1900, ranging from 132 in Croydon, Huddersfield and Halifax to 236 per 1000 births in Preston. Of 1000 male children born in England and Wales in 1881-90, the number surviving at the age of three months was 921, at the age of six months 889, twelve months 839, while the number of female children surviving one year of 1000 born was 869. In towns a smaller number survive. Of the conditions causing this high infantile mortality, ignorance and inexperience on the part of parents bear a considerable part, especially as influencing the food and mode of feeding. The death-rates at other age-groups beyond infancy are given in the table on page [340]. Season influences the death-rate. The third quarter of the year has the lowest death-rate, unless the amount of Epidemic Diarrhœa has been excessive. In the first quarter of the year, the highest death-rate usually occurs. Mild winters and cool summers both lower the mortality. The seasonal incidence of infectious diseases need only be mentioned in passing.
Density of Population has important bearings on the death-rate. Thus the urban districts in 1899 had a death-rate of 19·2 and the rural of 16·3 per 1000 of population. Farr found that the death-rate increased with the density of populations, not in direct proportion, but in proportion to the 6th roots of the contrasted populations. This rule does not now hold generally good. It is only after the density has reached a certain degree of intensity that it begins to exert an appreciable effect. Even then it is what is implied in aggregation rather than the aggregation itself that is pernicious. In particular, poverty is usually greater in densely populated districts than elsewhere, with its accompaniments of deficient food and clothing and bad housing. Hence the excess of phthisis in tenemented houses, especially in houses with only three rooms. I have shown that the true density that should be considered is the number of persons to each room, not the number of persons on a given area (“The Vital Statistics of the Peabody Buildings,” Roy. Statist. Soc., Feb., 1891).