Sex Ratio in AP Human Geography

The expected pattern: about 105 at birth, falling with age

The baseline claim is simple. Slightly more boys than girls are born almost everywhere, so the natural sex ratio at birth is roughly 105. After birth, males die at higher rates at most ages, and women tend to outlive men. The ratio slides toward 100 through adulthood and drops well below 100 in the oldest age groups.

The math is easy without a calculator. A town with 2,100 males and 2,000 females has a sex ratio of 105. The UAE has a population that is roughly two-thirds male, which works out to a ratio around 200, meaning about two males for every female. That number is far outside the natural range, so it needs a geographic explanation.

Using a skewed ratio as evidence of migration, policy, or war

A ratio near 200, like the UAE's, doesn't happen naturally, and explaining numbers like that is the point of Topic 2.3: Population Composition in Unit 2: Population and Migration. The course asks how geographers describe a population's makeup and why that makeup differs from region to region. A skew is evidence, so when a number strays from the natural pattern, your job is to name the process that caused it.

• Male labor migration. Gulf states like the UAE and Qatar draw large numbers of male workers for construction and oil-related jobs. Their population pyramids show a huge bulge on the male side in the working ages.
• Son preference. In parts of China and India, cultural preference for sons combined with sex-selective abortion pushed sex ratios at birth well above 105. China's one-child policy intensified this, which ties the term to population policy later in Unit 2.
• War and male mortality. Wars kill far more men than women. The Soviet Union had a large female surplus after World War II, and Russia still has many more women than men in older ages, partly because male life expectancy there is low.

The pattern also runs the other way. Places that send male workers abroad can end up with more women than men in the working ages, so the same migration stream leaves a mark on both ends.

Where one national number hides the real pattern

The limit of the measure is that a single national ratio averages out a lot. A country can look balanced while its regions are not. Mining towns, oil fields, and military bases often skew male. Some large cities attract more young women for service and office jobs, and retirement areas skew female because of older residents.

That's why sex ratio can be mapped and analyzed at different scales. Mapping Nigeria's sex ratios by its 36 states is a subnational analysis. Mapping Texas by its 254 counties, or Iowa by its 99 counties, is a finer, more local analysis that can expose differences between farm counties and urban counties that a state total would hide.

The second limit is that the ratio describes, it doesn't explain. A ratio of 120 tells you something happened, but you still need other evidence, like a pyramid, migration data, or policy history, to say what.

Reading sex ratio stimuli in multiple choice and Questions 2 and 3

A pyramid with a big male bulge in the working ages, like a Gulf state's, is the kind of stimulus to expect, along with maps and data tables. The question then asks which process best explains the skew. A question may also ask you to identify the scale of analysis used in a map or data set, so check what unit the data is collected in (country, state, county).

On the free-response section, sex ratio fits naturally into Question 2 (One-stimulus question) or Question 3 (Two-stimuli question) when the stimulus is a pyramid, a data set, or a map. A strong answer does three things: identifies the skew with a number or a described side of the pyramid, names a specific cause such as male labor migration, and explains a consequence, like a shortage of marriage partners or a large share of workers sending remittances home. At least two of the three free-response questions require analysis across geographic scales, so be ready to compare a national ratio with a regional one.

Sex ratio vs. dependency ratio vs. gender ratio

The biggest mix-up is with dependency ratio. Sex ratio compares males to females. Dependency ratio compares people under 15 and over 64 to the working-age population, and it ignores sex completely. If a question compares sexes, it's sex ratio; if it compares age groups, it's dependency ratio.

Gender ratio is often used as another name for the same male-female comparison, so treat the two as matching unless a question clearly says otherwise. Also keep the direction straight. A ratio below 100 means more females, which trips people up when they assume a bigger number always means a larger female share.