PREFACE In the following pages we have attempted to describe, with as little technicality as possible, the usual methods of constructing mortality and similar tables. As this book is intended mainly for those who have little or no acquaintance with the subject, we have tried to explain each step verbally with the help of arithmetical examples, in order to avoid the introduc- tion of algebraical formulae. It seems to us that such formulae are of little use in explaining the principles of the subject to beginners. We have tried to avoid debatable points, but we feel that in some directions the subject has not yet been advanced beyond the empirical stage. This is particularly true of the treatment of census data. Much work has been done in perfecting the details of the census methods, but their bases rest on very weak foundations, and it seems that until fuller and more accurate information is available the value of the assumptions at present made cannot be properly determined. vi PREFACE In conclusion, we desire to record our indebtedness to our friend J. A. Humphreys for many valuable suggestions. He most kindly offered to read the book again in proof, but his sudden death has de- prived us of this further help. "W. P. E. FBBBUABT 1914. R. c. p.