Intermediate Variable Framework Of Davis and Blake

Davis and Blake (1956)3 identified a set of 11 'intermediate variables' which directly affect fertility which they grouped into the following three categories. Bongaarts (1978) further refined the list of proximate determinants.

Factors Affecting Intercourse Variables

A. Those governing the formation and dissolution of unions in the reproductive period

1. Age of entry into sexual unions
2. Permanent celibacy: proportions of women never entering sexual unions
3. Amount of reproductive period spent after or between unions
   1. When unions are broken by divorce, separation, or desertion
   2. When union are broken by death of husband

B. Those governing the exposure to intercourse within union

4. Voluntary abstinence
5. Involuntary abstinence (from impotence, illness, unavoidable but temporary separations)
6. Coital frequency (excluding periods of abstinence)

Factors Affecting Conception Variables

7. Fecundity or infecundity, as affected by involuntary causes
8. Use or non-use of contraception
9. Fecundity or infecundity, as affected by voluntary causes

Factors Affecting Gestation Variables

10. Foetal mortality from involuntary causes
11. Foetal mortality from voluntary causes

In the process of child bearing three stages may be easily identified:

1) Intercourse

2)Conception 

3) Gestation and Parturition 

 Series of Physiological Events in Child Birth

Though these process are biological in nature, it is affected by social, cultural and economic factors. The way in which the non- physiological factors affect fertility in any society may be explained on the basis of the widely acclaimed model devised by kingsley Davis and Judith Blake. Various studies on fertility levels and trend in different population groups revealed substantial difference in fertility levels among various socio - economic groups. Analysing such differentials, Davis and Blake (1950) described the concept of 'intermediate variables' a set of "factors through which and only through which social economic and cultural conditions can affect fertility ".

Intercourse Variables: 

The variable mainly included those which are related to the formation and dissolution of families ( union) through marriage , through pre-marital sexual practices may aslo be included in this group. In most societies, sexual intercourse and child bearing are premitted only to married couples. Among the various variables determining the formation and dissolution of Martial unions, the female age at marriage and the proportion of those who never married in the reproductive age group are important because they have major share in determining fertility levels and differential. The duration of the period spent in the reproductive age acquires importance in its effect on fertility. 

Voluntary Abstinence:

One cultural factor responsible for keeping the level of fertility low covers the traditional practices which are followed for governing the sex life of married couples. They include the separation of women after child birth the custom of sending the woman to her parents home for the first delivery, taboos in sex relations when the child is young and certain religious days. Of particular interest is fact that the number of days on which sexual intercourse is prohibited varies from about 80 days to 100 in a year for the Hindus.

Foetal Morality by Voluntary Causes

Women have restored to the practice of induced abortion to get rid of unwanted pregnancies. For eg in Japan, the Eugenic Protection Law of 1948 permitted induced abortion  under certain conditions, Japanese women restarted to induced abortion on a very large scale. As a result the birth rate in Japan declined rapidly. 

Use of Contraception Including Sterilisation 

The use of birth control methods has been the most important intermediate variables responsible for the decline in fertility in various western countries in the later part of the nineteenth century and twentieth century. From the experiences of various countries it is apparent that the effective use of contraceptives is most important variables affecting the fertility of any society.