| Chapter 2: | Background and Theoretical Development |
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duration of time between the last live birth and the survey date for any married woman in the reproductive age group surveyed at a particular point of time. The duration between consummation of marriage and birth of first child is termed a closed birth interval. The duration between two consecutive births also is termed a closed birth interval. Several studies have used these concepts to observe changes in fertility levels (Feeney & Ross, 1984; Guilkey, 1988; Koenig, Phillips, Campbell, & D’Souza, 1990; Palloni, 1984; Pandey & Suchindran, 1997; Smith, 1985; Srinivasan, 1968, 1970; Trussell et al., 1985).
Several probabilistic and abstract concepts are also used to measure fertility. One of these is called the parity progression ratio, defined as the “probability that a married woman reaching parity i will ever progress to parity i+1 in her reproductive span” (Srinivasan, 1970, p. 401). Several studies have adopted this probabilistic concept to measure fertility levels (Feeney, 1983; Feeney & Yu, 1987; Hosseini-Chavoshi, McDonald, & Abbasi-Shavazi, 2006; McClelland, 1979; Rodriguez & Trussell, 1981; Sheps & Perrin, 1964). One of the advantages of this method is that it measures both the quantum and tempo of fertility in a society; that is, it takes into account the proportion of women moving from a lower parity to a higher parity as well as the rate at which women are progressing to a higher parity.
Researchers have also used several other fertility indicators, such as the marital fertility rate (Cleland & Rodriguez, 1988; Knodel, 1979; Tolnay, 1981), defined as the number of children born to married women in the 15–49 age group, and crude birth rates (Guest, 1974; Nortman, 1978; Yi, Ping, Liu, & Ying, 1991). Overall, the indicators of fertility just discussed have always measured a single outcome of the reproductive process, namely, the children ever born. The concept of reproductive health, on the other hand, takes into consideration the entire reproductive