Sex Ratio of Potential First-Marriage Partners
One of the commonly used indices to estimate the marriage squeeze is the sex ratio, and many studies restrict the population studied to a small age range (Goldman et al. 1984; Lampard 1993; Ebenstein and Sharygin 2009). One advantage of such indices lies in their easy calculation, but they only estimate the sex ratios of age-specific groups or the number of surplus males for a specific age difference between males and females. In reality, the range of ages at marriage is quite wide. Tuljapurkar et al. (1995) used the sex ratio of potential first-marriage partners to predict the tightness of China’s marriage squeeze. Under the assumption that first-marriage frequencies and patterns for the years subsequent to the baseline year remain unchanged, the index was computed as the ratio of the age-specific number of males, weighted by the age-specific first-marriage frequencies for males, to the age-specific number of females, weighted by the corresponding frequencies for females. The age-sex-specific first-marriage frequencies in a given year are defined as the ratios of the numbers of first marriages of the specific ages and sex during a certain period to the corresponding total population of the same ages and sex. Jiang et al. (2011b) attempted to improve this index by eliminating the tempo effect (the influence of change in event timing, such as advancing or delaying marriage, on statistical indicators (Bongaarts and Feeney 1998, 2002) on first-marriage frequencies and by normalizing the total first-marriage rates for both sexes, because they are well below unity. However, these revised indicators also do not consider marital status. An example will help to illustrate our focus in this paper. If 120 males and 100 females are born, then the general sex ratio is 120 males to 100 females in the marriage market without considering gender differentials in mortality. After 80 couples are married there are 40 males and 20 females left in the marriage market. For these never-married males, the marriage pressure is much more severe than that experienced by the whole population without considering their marital status.
Before introducing our new index, we first distinguish two kinds of age-specific first-marriage rate. The first-marriage rate of the first kind (occurrence/exposure rate) is the age-specific first-marriage rate for never-married persons, calculated as the ratio of the number of first marriages in an age group to the never-married population in the same age group. These age-specific first-marriage rates can be used to construct a nuptiality table from which we can derive the proportions never married up to different ages, and the mean duration of stay in the unmarried state for those who ultimately marry, namely the mean age at first marriage. The second kind of first-marriage rate is the ratio of the number of age-specific first marriages to the total population in that age group, which is also called the first-marriage frequency. As the married population is not exposed to the risk of first marriage, and the competition in the first-marriage market will only be faced by the never-married population, the second kind of first-marriage rate obscures or even distorts the demand and supply relationship in the marriage market. Here, we devise a sex ratio to measure the marriage squeeze for those who never marry.
We denote the number of males and females of age x in the year t in the whole population by P
m,x
t
and P
f,x
t
, respectively; the number of never-married males and females by \({\text{NM}}_{t}^{m,x}\) and \({\text{NM}}_{t}^{f,x}\), respectively; and first-marriage rates of the first kind by \({\text{FMR}}_{t}^{m,x}\) and \({\text{FMR}}_{t}^{f,x}\) for males and females, respectively. In demography, a person who is never married by age 50 is regarded as lifelong never married, so we restrict our age range for first-marriage rates from 14 to 49. Taking the year 2000 as the baseline year, the sex ratio of potential first-marriage partners can be expressed intuitively as R
′
t
:
$$R_{t}^{{^{\prime } }} = \frac{{\sum\nolimits_{x = 14}^{49} {{\text{NM}}_{t}^{m,x} \times {\text{FMR}}_{2000}^{m,x} } }}{{\sum\nolimits_{x = 14}^{49} {{\text{NM}}_{t}^{f,x} \times {\text{FMR}}_{2000}^{f,x} } }}. $$
(1)
This index has the following defects. First, it does not take into account the influence of the relative number of males and females in the baseline year. Without considering the two-sex problem, and remarriage, we assume the number of never-married males of each age in the baseline year is twice that of females, and that first-marriage rates of the first kind for males of each age are one-half of those for females. The calculated sex ratio of potential marriage partners in the baseline year is one, indicating that the number of male first marriages in this year equals that of females. However, since there are twice as many marriageable never-married males, males are severely squeezed in the marriage market. Obviously, the sex ratio of one in this example fails to reflect the severity of marriage squeeze. A second flaw lies in the use of age-specific first-marriage rates of the first kind obtained directly from the census data, which may be affected by many other factors. In fact, if we replace the first kind of first-marriage rates by the second kind in the year 2000, we can calculate the total first-marriage rates in 2000, denoted by \({\text{TFMR}}_{2000}^{m}\) and \({\text{TFMR}}_{2000}^{f}\), respectively, namely:
$${\text{TFMR}}_{2000}^{m} = \sum\limits_{x = 14}^{49} {{\text{FMR}}_{2000}^{m,x} } /({\text{NM}}_{2000}^{m,x} /P_{2000}^{m,x} ) = 0.736$$
$${\text{TFMR}}_{2000}^{f} = \sum\limits_{x = 14}^{49} {{\text{FMR}}_{2000}^{f,x} } /({\text{NM}}_{2000}^{f,x} /P_{2000}^{f,x} ) = 0.780.$$
In addition to underreporting of first marriages and increase in the lifelong never-married proportion, which contribute to the low total first-marriage rates for males and females from the 2000 census data, another important contributor may be the tempo effect in marriage. In 1975, the mean age of brides’ first marriages was from 22 to 24 in some Western countries, but in the mid-1990s it was between 26 and 29 years, and the mean age of males’ first marriages was also higher (Kiernan 2001). Older age at marriage can explain the sharp fall in marriage rates in Western countries (Winkler-Dworak and Engelhardt 2004). Coale et al. (1991) noted the effect of changes in marriage ages on period first-marriage rates in China. When the mean age at first-marriage rises, the total first-marriage rate falls in the corresponding period of time, and the opposite occurs if there is a fall in the age at first marriage. Therefore, the observed TFMR, which is affected by delayed or advanced timing of marriage, fails to reflect the lifelong completed total first-marriage rate for a specific cohort. In addition, if \({\text{FMR}}_{2000}^{f,x}\) is used, the estimated lifelong never-married proportion for females is \(\prod\limits_{x = 14}^{49} {(1 - {\text{FMR}}_{2000}^{f,x} } ) = 0.012\). In fact, the actual proportions of women never married at ages 45–49 in 2000 in China are 2.24, 2.25, 1.98, 1.90, and 1.85 per thousand, respectively. The estimate 0.012 is five to seven times higher than the actual proportions.
There would be a discrepancy in the results if the age-specific first-marriage rates obtained in the baseline year 2000 applied directly, so it is necessary to adjust those rates. We take \(c_{m}\) and \(c_{f}\) as normalizing coefficients for males and females, and normalize the total first-marriage rates in the baseline year 2000 as follows:
$$\begin{gathered} {}_{\text{norm}}{\text{TFMR}}_{2000}^{m} = c_{m} \sum\limits_{x = 14}^{49} {{\text{FMR}}_{2000}^{m,x} } /(NM_{2000}^{m,x} /P_{2000}^{m,x} ) = 1, \\ {}_{\text{norm}}{\text{TFMR}}_{2000}^{f} = c_{f} \sum\limits_{x = 14}^{49} {{\text{FMR}}_{2000}^{f,x} } /({\text{NM}}_{2000}^{f,x} /P_{2000}^{f,x} ) = 1 \hfill \\ \end{gathered}$$
The female lifelong never-married proportion is \(\prod\limits_{x = 14}^{49} {(1 - c_{f} {\text{FMR}}_{2000}^{f,x} } ) = 0.0033\) from 2000 census data after normalization, which is closer to those for females aged 45–49 in 2000 than the above estimate of 0.012. Then, assuming women’s first-marriage rates do not change from 2000 to 2060, the sex ratio of future potential first-marriage partners is:
$$R_{t} = \frac{{\sum\nolimits_{x = 14}^{49} {{\text{NM}}_{t}^{m,x} \times c_{m} \times {\text{FMR}}_{2000}^{m,x} } }}{{\sum\nolimits_{x = 14}^{49} {{\text{NM}}_{t}^{f,x} \times c_{f} \times {\text{FMR}}_{2000}^{f,x} } }} = R_{t}^{'} (c_{m} /c_{f} ). $$
(2)
Here R
t
is employed to measure the marriage squeeze. We can see that this indicator is different from those in previous studies (Tuljapurkar et al. 1995; Jiang et al. 2011a, b) in that it takes into account only the never-married population when calculating the tightness of the marriage squeeze as it is the never-married who face the pressure in the marriage market. In order to trace the never-married population, we use a longitudinal simulation method, distinguishing the population in the baseline year by age, sex, and marital status (two categories, namely never-married and others), and then project them to the next year using demographic parameters.
In reality the number of male marriages should equal that of female marriages, namely,
$$\frac{{\sum\nolimits_{x = 14}^{49} {{\text{NM}}_{t}^{m,x} \times {\text{FMR}}_{t}^{m,x} } }}{{\sum\nolimits_{x = 14}^{49} {{\text{NM}}_{t}^{f,x} \times c_{f} \times {\text{FMR}}_{2000}^{f,x} } }} = 1$$
where c
f
is computed as above from 2000 census data. Assuming the age-specific first-marriage rates for males are scaled by the same factor, we can estimate the age-specific first-marriage rates in a specific future year as \({\text{FMR}}_{t}^{m,x} = {{c_{m} \times {\text{FMR}}_{2000}^{m,x} } \mathord{\left/ {\vphantom {{c_{m} \times {\text{FMR}}_{2000}^{m,x} } {R_{t} }}} \right. \kern-0pt} {R_{t} }}\). Then we can obtain \({\text{NM}}_{t + 1}^{m,x + 1}\) as
$${\text{NM}}_{t + 1}^{m,x + 1} = {\text{NM}}_{t}^{m,x} \times (1 - {\text{FMR}}_{t}^{m,x} ) \times {{L_{x + 1} } \mathord{\left/ {\vphantom {{L_{x + 1} } {L_{x} }}} \right. \kern-0pt} {L_{x} }} , $$
(3)
where L
x
is the person years aged from x to x + 1 in the life table. We apply the relationship between rate and probability (Keyfitz and Caswell 2005) to obtain the probability q
m,x
t
that a male’s first marriage occurs at time t when his age is x: \(q_{t}^{m,x} = {{2 \times {\text{FMR}}_{t}^{m,x} } \mathord{\left/ {\vphantom {{2 \times {\text{FMR}}_{t}^{m,x} } {(2 + {\text{FMR}}_{t}^{m,x} )}}} \right. \kern-0pt} {(2 + {\text{FMR}}_{t}^{m,x} )}}\).
We can find the probability of first marriage, and then construct annual nuptiality tables for males.
Lifelong Never-Married Proportion for Males
We use two methods to estimate the proportion of lifelong never-married at each time t. One is based on the population projection: from formula (3) we can calculate the age-specific never-married proportion in future years, and take \(\left[ {{{{\text{NM}}_{t}^{m,50} } \mathord{\left/ {\vphantom {{{\text{NM}}_{t}^{m,50} } {P_{t}^{m,50} }}} \right. \kern-0pt} {P_{t}^{m,50} }}} \right] \times 100\) at age 50 as the lifelong never-married percentage. This result applies for every birth cohort when they reach age 50; thus it can be regarded as a cohort indicator. The other way is to obtain the proportion through the generated male nuptiality tables: \(l_{50} = \prod\limits_{x = 14}^{49} {(1 - q_{t}^{m,x} } )\) in each year, where l
50 is the proportion of men who never married by age 50 in a nuptiality table, and q
m,x
t
is the first-marriage probability of men aged x at time t. As probabilities for all ages in the nuptiality table are obtained for that year, the proportion never-married can be regarded as a period indicator.
Mean Age at First Marriage for Males
Two methods are used to calculate the mean age at first marriage for males. One is through the predicted population, from which we can obtain the never-married proportion by age, and derive the singulate mean age at marriage (SMAM). The sum of all the proportions of never-married men from ages 14 to 49 is
$${\text{RS}}_{1} = \left( {\sum\limits_{x = 14}^{49} {{\text{NM}}_{t}^{m,x} /P_{t}^{m,x} } } \right)$$
Define
$${\text{RS}}_{2} = {\text{RS}}_{1} + 14.0,$$
and denote the never-marrying proportion before the age of 50 as
$${\text{RM}} = 1.0 - {\text{NM}}_{t}^{m,50} /P_{t}^{m,50}.$$
Then the duration of singlehood for those never-married at age 50 is
$${\text{RS}}_{3} = 50.0 \; \times \;{\text{NM}}_{t}^{m,50} /P_{t}^{m,50},$$
and the singulate mean age at marriage is
$${\text{SMAM}} = \left( {{\text{RS}}_{2} - {\text{RS}}_{3} } \right)/{\text{RM}} .$$
Another method is to use 14 + e
14, which is based on the expected duration of singlehood e
14 at age 14 in the male nuptiality table.