Search results
Results from the WOW.Com Content Network
In the case of China, because of deficiencies in the vital statistics registration system, studies of sex ratios at birth have relied either on special fertility surveys, whose accuracy depends on full reporting of births and survival of both male and female infants, or on the national population census from which both birth rates and death ...
If the male fish dies, the strongest female changes its sex to become the male for the group. All of these wrasses are born female, and only become male in this situation. Other species, like clownfish, do this in reverse, where all start out as non-reproductive males, and the largest male becomes a female, with the second-largest male maturing ...
It shows the male to female sex ratio by the Central Intelligence Agency of the United States. If there is a discrepancy between The World Factbook and a country's census data, the latter may be used instead. A ratio above 1, for example 1.1, means there are more males than females (1.1 males for every female).
The replacement fertility rate is 2.1 births per female for most developed countries (in the United Kingdom, for example), but can be as high as 3.5 in undeveloped countries because of higher mortality rates, especially child mortality. [11]
In 2021, China's official census report showed a sex ratio of 112 male to 100 female births, compared to a global average of 105 or 106 male to 100 female births. This is down from a high of 118 male to 100 female births from 2002 to 2008. [2] The sex imbalance in some rural areas is higher, at 130 boys to 100 girls. [3]
In 2014, the ratio of female births per 1000 male births varied from 887 to 918 using these estimates. [6] According to the NFHS-4 (2015–16) sex ratio of the total population (females per 1,000 males) was 991 (with an urban ratio of 956 and a rural ratio of 1,009).
The U.S. birth rate has been steadily declining for years, but fairly recently it has tipped over into an alarming category. The estimated “replacement fertility rate,” or the number of births ...
The low birth rates in the contemporary United States can possibly be ascribed to the recession, which led families to postpone having children and fewer immigrants coming to the US. The current US birth rates are not high enough to maintain the size of the U.S. population, according to The Economist. [69] [70]