Data Licence Agreement  

The singulate mean age at marriage (SMAM) is the average length of single life expressed in years among those who marry before age 50.

  Method of computation

The singulate mean age at marriage is calculated from the proportions single by age.  
Step 1. Calculation of the person years lived in a single state, denoted by A:

where Sa is the proportion single in age group a.

Step 2. Estimation of the proportion remaining single at age 50, denoted by B:

B = (S45-49 + S50-54)/2

If the proportion single in age group 50-54,  S50-54, is not available, then

B = S45-49

Step 3. Estimation of the proportion ever marrying by age 50, denoted by C:

C = 1 - B

Step 4. Calculation of the number of person-years lived by the proportion not marrying, denoted by D:

D = 50*B

Step 5. Calculation of singulate mean age at marriage (SMAM):

SMAM = (A - D)/C

Statistical system generating the data


Data on the population by age group, sex and marital status are generally obtained from censuses or sample surveys that include questions regarding the current marital status, age and sex of persons enumerated. Data derived from censuses are generally preferred because, when obtained through a questionnaire applied to the whole population, they are not affected by sampling variability.  However, reporting errors may nevertheless bias the results.


Sources of the data presented


Data derived from censuses are generally reported by National Statistical Offices to the Statistics Division of the Department of Economic and Social Affairs of the United Nations Secretariat. Census data are also obtained from official census publications produced by National Statistical Offices. Adjusted data are only used when so reported by National Statistical Offices.

Survey programmes, such as the Demographic and Health Surveys (DHS) or the CDC-sponsored Reproductive Health Surveys (RHS), as well as national surveys are sources of the data required to calculate the percentages of ever married persons by age and sex.

In World Marriage Data 2008, estimates derived from a single source are presented for each reference year. In cases where more than one source could yield the required estimates, preference is given to estimates based on population censuses. In cases where the estimates can be derived from different surveys carried out the same year, preference is given to those derived from the larger survey.

For each data point included in the data files, information on the type of statistical system generating the data (census, survey) and on the exact source of the data (usually denoted by an acronym) is provided. The meaning of each acronym used is presented in the worksheet labeled "Sources". For surveys that are not part of an international survey programme, the full name is provided in the field "Survey name".

  Comments and limitations

The estimates by age may be affected by age misreporting. Marital status may be misreported, particularly in societies where divorce or separation is not socially acceptable. Data derived from surveys with small samples may be significantly affected by sampling variability.


Data coverage and reference years for the data reported

  World Marriage Data 2008 contains data on the singulate mean age at marriage by sex for 214 countries or areas.  When available, data are presented for five reference dates: the closest years to 1970, 1985 and 1995, and the two most recent available years after 1999. Data for all the five reference dates are available for 59 countries or areas.  


  Suggested citation:
United Nations, Department of Economic and Social Affairs, Population Division (2009). World Marriage Data 2008 (POP/DB/Marr/Rev2008).