“The baby boom and its explanations.” The Sociological Quarterly, 24(3), 353-365.

2 main trends in fertility in the postwar era

1.  Increase in fertility through the late 1950s (baby boom)

2. Rise in frequency and effectiveness of contraception during the 1960s

Demographic features of the baby boom

- The TFR was about 2.2 during the mid-1930s, 3.6 during the baby boom, ad 1.8 during the mid-1970s

- Ryder (1980) demonstrated that the period fertility rate can change even if the cohort fertility rate remains unchanged

- He showed that the increase in period fertility was due more to the timing of births than the changes in quantum

- However, not a significant portion of the baby boom was still due to quantum

- Much greater proportion of women having two children (82% of 1933 cohort had at least 2 kids), rather than some families with at least two children going on to have more

In sum, the baby boom consisted of the following 4 phenomena:

1. Women marrying and having first births earlier after the war

2. A larger proportion of women having at least 2 kids

3. A larger proportion of women having families of the same size (2-4 kids)

4. A slight increase in average family size, owing to increases in unintended fertility

Explanations for these patterns

- Shift toward values of family and traditionalism

- Post-war economic prosperity

- Social-psychological effects of growing up during the depression (Elder)

- Easterlin hypothesis that cohort size affects relative economic status (small cohorts during depression)

“On the quantum and tempo of fertility.” Population and Development Review, 24(2), 271-291.

The main advantage of the period TFR is that it measures current age-specific fertility and therefore gives up-to-date information on levels and trends

-In addition, it is simple to interpret

Main disadvantage is that it doesn’t reflect the actual experience of any cohort of women

- Although the cohort TFR has the advantage of representing the actual fertility experience of a group of women, it has the disadvantage of representing past experience because women currently age 50 did most of their childbearing decades ago

The purpose of this paper is to develop a measure of the period TFR that is free of tempo effects (distortions due to changes in the timing of births)

- This will measure just the quantum component of the TFR (the TFR that would have been observed in the absence of changes in the timing of births)

- New measure called the tempo-adjusted tempo-adjusted TFR

- The main problem to be dealt with is that a decreasing mean age at childbearing artificially inflates the TFR, whereas an increasing mean age at childbearing automatically deflates the TFR

- Bongaarts and Feeney derive the tempo-adjusted TFR by dividing the observed TFR at parity i by (1-r_i) where r_i is the change in the mean age at childbearing at order i during the year

- The tempo-adjusted TFR (TFR*) simply equals the sum of the parity-specific TFRs

- If the mean age at childbearing increases by 0.2 years, the number of births in year t will be 20% lower than they would have been in the absence of this change

- Likewise, if the mean age at childbearing decreases by 0.2 years, the number of births will by 20% higher

- It is easy to distinguish between tempo and quantum effects because tempo effects involve a change in the mean age at childbearing whereas quantum effects do not

Advantages of this method

- Only need data from one period

Challenges of method

- Need to be able to discern birth parity

Assumptions of this method

- Women of all ages bearing children in year t defer or advance their births to the same extent, regardless of age or cohort identification

- This assumption is likely violated during periods of war, famine, etc. when fertility changes rapidly from one year to the next and cohort effects are not negligible

In other words, period effects, rather than cohort effects, are the primary force in fertility change

“Tempo-adjusted period progression measures, fertility postponement, and completed cohort fertility.”

Authors point out that the quantum-tempo distinction involves a clear counterfactual—what levels of fertility would we observe in the absence of tempo effects

- However, tempo and quantum interact;

->delays in fertility likely also imply reductions in fertility

Showed that period fertility rate can change even if the cohort fertility rate remains unchanged

Showed that the increase in period fertility was due more to the timing of births than the changes in quantum

The second demographic transition to lowest low fertility hinges on the behavior of women with no or few births

(as opposed to shift from high fertility to low fertility regime during demographic transition mostly resulted from declining number of higher parity births).

“Timing effects and the interpretation of period fertility.” Demography, 41(4), 801-819.

Develops the average cohort measure (ACF) of fertility, which measures period fertility adjusted for timing effects

- Norman Ryder argued that fertility change should be analyzed from a cohort perspective

- In contrast, Bongaarts and Feeney take a period perspective with their tempo-adjusted TFR

- As a way to combine these perspectives, Schoen’s measure examines the fertility behavior of a period and assesses the extent to which that period has a disproportionate share of cohort fertility

- Develops a timing index (TI) to assess the extent to which the cohort fertility of women childbearing during year t occurs in year t

- If TI(t) =1 no timing effects are occurring

- If TI(t) < 1 year t contains disproportionately small amount of cohort fertility and

- If TI(t) >1 year t contains disproportionately large amount of cohort fertility

The average cohort fertility in year t ACF(t) = TFR(t) / TI(t)

- One major limitation of this method is that it requires knowledge of completed cohort fertility, which often isn’t available until long after women have children

- Schoen argues that the ACF performs better than Bongaarts and Feeney’s TFR* because the TFR* has the tendency to amplify some period behavior while at other times failing to capture the level and direction of fertility timing effects

TFR* performs better when there are long, gradual changes in the mean age at childbearing