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The Habitable PlanetHabitable Planet home page

Interactive Labs

Demographics Lab

Tools of the Simulator

Simulator Controls

Reset Button
Returns the simulator to year 2015. This does not reload the original parameter values (vital rates). To do that, you can either select another country and then re-select this country, or use the Reset button on the Birth or Death rate dialogs.
Pause Button
Stops the progression of the simulator at the moment it is clicked. Works with the Run button.
Step
Simulates the progression of population as determined by the parameters for 5 years.
Run
Simulates the progression of population as determined by the parameters to year 2050. After 2050, runs in increments of 50 years.

Simulator Parameters

COUNTRY
This pull-down menu allows you to choose a country from those included with the simulator.

Vital Rates buttons

Birth
This button is labelled with the current birth rate for the chosen country. Clicking on the button opens up a Change Birth Rates dialog that allows you to alter the birth rate.

Change Birth Rates dialog

On the Change Birth Rates dialog:
Use Rates From: Use the pull-down menu to choose any country modeled in the simulator to copy birth rates from. Click "Apply" to make rate changes active.
+/- 5%: Up/down arrow buttons allow you to change the birth rates by increasing or decreasing by 5 percent the average number of children born per age group per 5 years. The bar graph below is updated to reflect the change.
- 5 years/+ 5 years: Right/left arrow buttons allow you to change the average age of child-bearing women by shifting the bar graph rates right or left by 5 years.
Result: The brown box to the right of the arrow buttons shows the new average children per lifetime resulting from choices on this dialog, and average mother age—a weighted average of the number of children born at each age group and the probability of a woman living to reach that age group and bear children.
Bar Graph: Shows the average number of children born in 5 years to members of each 5 year age group.
Reset: Reloads the original birth rates for the current country.
Death
This button is labelled with the current death rate per capita for the chosen country. Clicking on the button opens up a Change Death Rates dialog that allows you to alter the death rate.
Note that birth rate per woman per lifetime, as labelled on the button, stays constant from Step to Step, but the death rate changes each Step. That's because the death rate per capita depends on both the age-specific death rates, and the current shape of the population pyramid. For instance, when more people are over age 60, the overall death rate rises. Also if death rates change, the birth rate per woman per lifetime changes, because more or fewer women may live to a particular age to bear children.

Change Death Rates dialog

On the Change Death Rates dialog:
Use Rates From: Use the pull-down menu to choose any country modeled in the simulator to copy death rates from. Click "Apply" to make rate changes active.
+/- 50%: Up/down arrow buttons allow you to change the death rates by increasing or decreasing by 50 percent the average number of deaths per 5 year age group over 5 years. The bar graph below is updated to reflect the change.
- 5 years/+ 5 years: Right/left arrow buttons allow you to change the death schedule by shifting the bar graph rates right or left by 5 years.
Result: The brown box to the right of the arrow buttons shows the per capita death rate per year resulting from choices on this dialog. This is the same number used to label the Death button that opens the dialog.
Bar Graph: Shows the percentage of people who die during their 5 years in each age group.
Reset: Reloads the original death rates for the current country.
Growth
Reports the current population growth rate per year. This is updated after each Step. A negative growth rate means the population is decreasing.

Population (millions) Line Graph

This graph shows a time series of population growth for the selected country. The y-axis is the population (in millions) of that country for the year displayed on the x-axis. You can mouse over or tap points on the lines for a tooltip giving the line value at that point. The overall current population is also reported in the top right corner of the plot. Clicking on a line in the legend turns it on or off.

Population graph, Iraq

On the graph:
Projected: Represents the population of the selected country as projected by the US Census International Database. (See Unit 5 text, Section 3).
Although the IDB uses a similar model to this Demographics simulator, the projected (grey) lines are often different than the simulated (red) lines. This is because the IDB projection incorporates migration and continuing shifts in birth and death rates. For example, in the plot above, of Iraq, the IDB likely forecast decreasing birth rates and increased emigration to account for 9 million in lower population than that simulated by this Demographics simulator for year 2050. This discrepancy is most striking in the case of Italy, where the IDB Projected line expects the population of Italy to stabilize. But Italy's current birth rates, death rates, and population structure dictate the population fall sharply. In Italy's case, the IDB likely forecast massive immigration.
Simulated: Represents the population as simulated with the current provided birth and death rates. No migration.
Age 65+: Represents the population of the older age groups.
Now: The diamond on the line highlights the current year and simulated population.

Population Pyramid, Nigeria

Population By Age Group (millions)

This graph shows the population (as number of people in millions), per age group by gender. This is called a “population pyramid”. The blue bars represent the numbers of males and the pink bars represent the numbers of females in each age group. The overall population is the sum of all bars.

Early in the demographic transition, the base of the pyramid is much wider than the top, as in this plot of Nigeria. With a dwindling population, as with Italy and Japan, the pyramid shape may invert, with the largest age groups toward the top.

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