Population Growth

Total population change combines natural increase with net migration. First calculate natural increase by subtracting deaths from births: \(8500-5900=2600\). Next calculate net migration by subtracting out-migrants from in-migrants: \(2100-3200=-1100\). The negative sign means the region lost 1100 people through migration.

Combining both components gives \(2600+(-1100)=1500\), so the total population increased by 1500. The value 2600 ignores migration, while 1100 is only the migration loss. A result of 3700 would incorrectly add all positive figures without subtracting deaths and out-migration. Therefore option A is correct.

An annual growth rate is a percentage of the starting population, not a fixed number of people. To calculate the one-year increase, convert 1.35 percent to the decimal \(1.35/100=0.0135\), then multiply it by the population of 90 million. This gives a simple estimated increase for one year.

The calculation is \(90000000\times0.0135=1215000\). Therefore, the population grows by approximately 1,215,000 people, so option C is correct. The word “approximately” reflects the simple percentage calculation and does not require a more complex compounding model for this one-year estimate. Treating 1.35 as a number of people, rather than a percentage, would be incorrect.

Percentage growth is calculated using the increase divided by the original population, multiplied by 100. The population rises from 25 million to 32 million, so the absolute increase is \(32-25=7\) million. The original population, 25 million, is the base for calculating the percentage; the final population is not used as the denominator.

Thus percentage growth is \((7/25)\times100=28\%\). Therefore option C is correct. The increase is not 32%; that is the final population expressed in millions. It is also not 24% or 26%, because those values do not result from comparing the 7-million increase with the original 25-million population.

A total increase of 36 percent is measured relative to the initial population. Therefore, if the initial population is represented as 100 percent, the final population must be 100 percent plus 36 percent, or 136 percent of the initial population. This conclusion does not require knowing how the increase was distributed across the twelve years.

Hence option B is definitely correct. The data do not prove an exact annual rate of 3 percent; annual growth could vary, and compound growth would not equal a simple division in that way. They also do not reveal the birth rate or whether migration contributed. Only the final-to-initial relationship is certain.

Percentage growth is a rate, while absolute growth is the actual number of people added. Even a reduced percentage rate can produce a large numerical increase when it is applied to a very large population base. The base population may have expanded over time, so a smaller fraction of that larger base can be nearly equal to the earlier, higher-rate increase.

For example, 2% of 10 million is 200,000, while 1% of 20 million is also 200,000. Therefore option A is the strongest explanation: the population base has become very large. A zero death rate, doubled land area, or constant migration is not necessary and does not logically explain the stated relationship.

Total fertility rate measures the average number of children per woman, whereas the total number of births also depends on how many women are in the reproductive-age group. Fertility can therefore fall while births remain higher than expected if a large generation is currently entering or occupying reproductive ages. This temporary continuation is called demographic momentum.

For example, reducing the average births per woman does not immediately remove the large number of potential mothers. As those women have children, the total number of births may decline slowly rather than sharply. Death rate, migration, and land area do not provide the best explanation for this specific pattern. Therefore option A, a large reproductive-age population, is correct.

Total population growth combines natural change with net migration. Natural change is calculated by subtracting the death rate from the birth rate. Net migration is then added, with its sign showing whether migration adds to or subtracts from population. All rates here use the same unit, per thousand, so they can be combined directly.

Natural change is \(15-19=-4\) per thousand, meaning deaths exceed births by four per thousand. Adding net migration gives \(-4+6=+2\) per thousand. Thus the population still grows overall by 2 per thousand, because inward migration more than compensates for the natural decrease. Option C is correct; +6 per thousand alone ignores the natural component.

Natural increase and total growth are related but not identical. Total growth includes natural increase plus net migration. Therefore, net migration can be found by subtracting natural increase from total growth. A negative answer means that more people are leaving than entering, and it can reduce a positive natural increase.

Using the rates, net migration is \(2-11=-9\) per thousand. Thus the country has a negative net migration rate of 9 per thousand, so option B is correct. The calculation also checks because \(11+(-9)=2\). A positive value such as +9 would increase total growth to 20 per thousand and would not match the stated total.

Percentage growth compares the increase with the original population, not with the final population. First find the absolute increase by subtracting the starting population from the final population. Then divide that increase by the starting population and multiply by 100 to express it as a percentage.

The increase is \(6.05-5=1.05\) million. The percentage growth is \(1.05/5\times100=21\) percent. Equivalently, the final population is 1.21 times the original population, which represents a 21 percent increase. Therefore, option C is correct. Using the final population as the denominator would calculate a different measure and would not be the usual percentage growth from the starting value.

When a population grows by the same percentage every year, each increase is based on the previous year's population. This is compound growth. For an annual rate of 8 percent, the yearly multiplier is \(1+0.08=1.08\). Over three years, the initial population must therefore be multiplied by \(1.08^3\).

The calculation is \(2000000\times1.08^3\). Since \(1.08^3=1.259712\), the final population is \(2519424\), approximately 2.519 million. In lakh units, this is about 25.19 lakh. Therefore, option C is correct. Adding 24 percent once gives 2.48 million, but that ignores the fact that later increases apply to an already larger population.

Successive percentage changes must be applied one after another to the changing amount. They cannot be treated as a simple net change of 30 percent minus 20 percent, because the second percentage is calculated from the amount after the first change.

Take the initial population as 100. A 30 percent increase gives \(100\times1.30=130\). A 20 percent decline then leaves \(130\times0.80=104\). The final value is 104 compared with the original 100, so the net change is a 4 percent increase. Therefore, option A is correct. The difference of 10 percentage points would incorrectly use the same base for both changes.

Natural increase is found by subtracting the death rate from the birth rate. Since both values use the same unit, per thousand, no conversion is needed before subtraction. This calculation must be done for the original rates and again for the new rates to compare the change.

Initially, natural increase is \(35-13=22\) per thousand. After the rates change, it is \(25-9=16\) per thousand. Thus, natural increase falls from 22 to 16 per thousand, a decline of 6 per thousand. Option A is correct. Adding birth and death rates would measure neither natural increase nor natural growth, because deaths have a reducing effect on population.

People aged 20 to 34 are commonly important for both employment and family formation, although individual patterns differ across societies. If many people in this age group leave the country, fewer potential parents remain in the population. This can reduce the number of births in future years and weaken the country’s ability to convert its large young population into continued population growth. The effect may also reduce the working-age base.

Option A is correct because heavy out-migration removes a key reproductive-age group and can lower future births and growth potential. Option B is too absolute: demographic momentum will not always increase when many young adults leave. C is incorrect because the age-selective migration clearly changes population composition. D is unrelated and impossible to infer; migration does not make the death rate automatically zero. The precise effect depends on migrants’ family behaviour and duration abroad, but A is the best-supported choice.

Total population change can be written as natural change plus net migration. Here the natural change is \(-9000\), while net migration is \(+9000\). Their sum is \(-9000+9000=0\), so the total number of residents remains stable. However, a stable total does not mean that the same individuals or the same population structure remain.

Deaths may be concentrated among older residents, while incoming migrants may mostly be younger adults. As a result, the city can experience changes in age composition, social characteristics, skills, or cultural composition even though the headcount is unchanged. Therefore, option A is correct. The other choices either claim an impossible consequence or confuse stable total population with unchanged structure.

A natural increase rate of 18 per thousand means that 18 people are added naturally for every 1,000 people in the population during one year. The country has 24 million people, so the increase is \(24,000,000\times18/1,000=432,000\). Since migration is zero, this natural increase is also the total population increase for that year. Therefore option C is correct.

The calculation can be simplified because dividing 24,000,000 by 1,000 gives 24,000, and multiplying by 18 gives 432,000. The unit “per thousand” must be converted to the fraction 18/1,000, not 18/100. That distinction prevents a result one hundred times too large. Thus the annual natural increase is 432,000 people.

A natural increase rate of negative 4 per thousand means that, for every 1000 people, natural causes produce a loss of 4 people during the year. Natural change considers births minus deaths only; migration is not included unless separately provided.

Convert the rate to a fraction and multiply: \(48000000\times(-4\div1000)=-192000\). The negative sign indicates a decrease, so the natural change is a decrease of 192000 people. Hence option C is correct. The result is not 480000, because the rate is per thousand, not per hundred, and it is not a migration-adjusted total.

Total growth is obtained by adding natural growth and net migration. The signs must be preserved: a negative natural growth rate represents a decline, while positive net migration represents an addition. One should not add the absolute magnitudes, because that would ignore whether each component raises or lowers population.

The calculation is \(-1.2+1.7=+0.5\) percent. Therefore, the total population increases by 0.5 percent, even though natural growth is negative. Option C is correct. The result is positive because the 1.7 percent net inflow is larger than the 1.2 percent natural decline. The value +2.9 percent would incorrectly treat both numbers as positive contributions.

Total population growth combines natural increase and net migration. The relationship is \(\text{total growth}=\text{natural increase}+\text{net migration}\). To find net migration, rearrange it as \(\text{net migration}=\text{total growth}-\text{natural increase}\). Signs are important: positive natural increase must be subtracted as a positive number, while the total growth here is negative.

Substitute the values: \(-0.9-(+0.6)=-1.5\) percent. Thus the net migration rate is -1.5 percent, so option A is correct. The negative sign means that emigration exceeds immigration by 1.5 percent of the population under this rate description. The result is not -0.3 or a positive value; those would reflect incorrect handling of the signs.

Fertility decline affects the number of young children with a time lag. Children born before the decline continue to grow and reach primary-school age for several years. Therefore, school enrolment and demand may remain high even though the number of new births has begun to fall. Planning must consider these existing age cohorts rather than only current fertility.

The correct explanation is that large cohorts born earlier are still entering school ages. Hence option A is correct. Fertility decline does not immediately increase school-age children, and schools do not control birth rates. A zero death rate is also irrelevant to this delayed education-demand effect.

Age groups are cohorts that move forward through the population structure as time passes. A large group born in earlier years may later appear in the 25–44 age range. At the same time, if recent births are fewer, the number of children can decline. These two changes can happen together and are not contradictory.

Therefore option A is the best explanation. Earlier large birth cohorts are now entering adulthood, while lower current fertility reduces the child population. The other choices incorrectly assume that all age groups must move in the same direction or that changes occur immediately. Migration can also affect age structure, but the stated pattern is most directly explained by the movement of earlier large cohorts into adult ages.

Net migration is a numerical balance: arrivals minus departures. A net value of zero means the numbers entering and leaving are equal, but it does not mean the two groups have identical ages, education, or skills. Population composition can therefore change even when total population size remains unchanged.

Here, educated young adults arrive while older people leave. The country or city may consequently have a larger share of working-age people and a stronger skill profile. Thus option A is correct. Total population will not automatically double, and natural increase is not required to become zero. The example shows why demographic analysis must consider the characteristics of migrants, not only their net number.

The Rule of 70 is an approximate shortcut linking annual growth rate and doubling time. It states that doubling time in years is about 70 divided by the annual growth rate in percent. If doubling time is known, rearrange the relationship to find the rate.

Annual growth rate \(\approx70\div40=1.75\%\) per year. Therefore option C is correct. This is an estimate rather than an exact compound-growth calculation, but it is the intended use of the Rule of 70. A rate of 1% would imply a doubling time near 70 years, while 2.5% would imply about 28 years, so neither matches 40 years as closely as 1.75%.

Successive percentage increases are compounded because the second year's growth is calculated on the population after the first year's increase. Thus, a 9% increase corresponds to a multiplier of 1.09, and an 11% increase in the next year corresponds to a multiplier of 1.11.

The combined multiplier is \(1.09\times1.11=1.2099\). The final population is therefore 120.99% of the original, so the total two-year increase is 20.99%. Hence option B is correct. Simply adding 9% and 11% gives 20%, but that ignores the additional 11% applied to the population already enlarged by 9% in the first year.

A rapidly ageing country has a relatively large older population and may have a smaller working-age group. Young migrants are generally added to younger or working-age categories, so their arrival can increase the share of people able to work in the near term. This is a likely demographic effect, not an absolute guarantee about every individual migrant.

Therefore, option A is correct: the working-age ratio may increase. Young migration cannot immediately end population ageing, make births definitely double, or reduce the elderly population to zero. Its effect depends on the migrants’ ages, family patterns, length of stay, and the country’s wider demographic conditions.

Total population is the sum of all age groups, not just the working-age group. Therefore, total population can rise even when the 15–64 group falls. This may happen if the numbers of children or elderly people increase, or if many working-age adults migrate out. Changes in age cohorts can also alter the size of a particular group.

Thus, option A gives a valid explanation. For example, a large inflow of children or older people could raise total population while emigration reduces the working-age group. The other choices are incorrect because total growth does not require every age group to grow, and the working-age group is a distinct part of total population.