Direct standardization is used to compare the moality rates between two countries. This is done because of the difference in which of the following parameters?

Adjusted or Standardized rates are used to compare the death rates of two populations with different age composition. "Age adjustment" or "Age standardization" removes the confounding effect of different age structures and yields a single standardized or adjusted rate, by which the moality experience can be compared directly. The adjustment can be made not only for age but also for sex, race, parity, etc. Ref: Preventive and Social Medicine, By K.Park, 19th edition, Page 54, 55