The chart shows the number of deaths reported for 106 major cities of the United States by week for the current year, and, for comparison, the median of the number of deaths reported for the corresponding weeks of the three previous calendar years. (The median is the central one of the three values arranged in order of magnitude.) If a report is not received from a city in time to be included in the total for the current week, an estimate is made to maintain comparability for graphic presentation.

The figures reported represent the number of death certificates received in the vital statistics offices during the week indicated, for deaths occurring in that city. Figures compiled in this way, by week of receipt, usually approximate closely the number of deaths occurring during the week. However, differences are to be expected because of variations in the interval

between death and receipt of the certificate.

While week-to-week changes in the total number of deaths reported for all major cities generally represent a change in mortality conditions, this may not be true for variations in weekly figures for each city. For example, in a city where 50 deaths are the weekly average, the number of deaths occurring in a week may be expected to vary by chance alone from 36 to 64 (d 2Vd, where d represents the average number of deaths per week).

The number of deaths in cities of the same size may also differ because of variations in the age, race, and sex composition of their populations, and because some cities are hospital centers serving the surrounding areas. Changes from year to year in the number of deaths may be due in part to population increases or decreases.

712 3,415 2,427

973 876 462 909

742 3,300 2,517

928 966 557 845

721 3,007 2,177

-1.2 +13.6 +11.5 +27.0 +18.4 +12.4 +21.2 +49.5 +2.9

2,172 9,947 7,402 2,783 2.694 1,512 2,764

2,093 9,605 6,629 2,477 2,370 1,348 2,415

+3.A +4.0 +11.7 +12.4 +13.7 +12.2 +14.5 +34.0 -0.7