Changing the Data Display

Displays the average offspring per time interval per individual, as a function of age. Also allows you to change these values by clicking on the points you wish to set, by dragging the curve into the shape you want, or by clicking on the arrow buttons in the "tool bar" at the top of the window. The button on the left shifts the graph to the left. The button on the right shifts the graph to the right. The center button allows you to multiply all values on the y-axis by a constant amount.

NOTE: If you hold the mouse button down momentarily while over one of the arrow buttons, a dialog box will appear giving you more control over manipulating the graph.

The current position of the cursor is displayed in the box on the lower left of the graph.

The scale on the y-axis can be changed to allow for fertility values higher than 1.000. To increase the scale, position the cursor near the top of the graph over the age group that you want to change. The shape of the cursor will change from the cross-hair to an arrow pointing straight up. Clicking the mouse will cause the y-axis to rescale. To reduce the scale, simply reduce all the values of the fertility curve. The y-axis will automatically readjust.

To see this graph, if it is not already shown, choose the ìFertility vs. Ageî command from the Display-type menu.The data can be displayed as a graph, as a bar chart, or as a table.

Displays the probability that an individual from any age interval will die during the current time interval. Also allows you to change these values by clicking on the points you wish to set, by dragging the curve into the shape you want, or by clicking on the arrow buttons in the "tool bar" at the top of the window. The button on the left shifts the graph to the left. The button on the right shifts the graph to the right. The center button allows you to multiply all values on the y-axis by a constant amount.

NOTE: If you hold the mouse button down momentarily while over one of the arrow buttons, a dialog box will appear giving you more control over manipulating the graph.

The current position of the cursor is displayed in the box on the lower left of the graph.

To see this graph, if it is not already shown, choose the ìMortality vs. Ageî command from the Display-type menu.The data can be displayed either as a graph or as a table.

Displays the probability that an individual will survive from age zero to a given age. The values displayed are calculated from the mortality values; you cannot change this window directly. Notice that survivorship curves are decreasing (or at least non-increasing) functions of age.

To see this graph, if it is not already shown, choose the ìSurvivorship vs. Ageî command from the Display-type menu.The data can be displayed either as a graph or as a table.

Displays the percentage of total population or the total number of individuals currently in each age interval (males are on the left, in blue; females are on the right, in red). Also allows you to change the number or percentage of population in each age interval by clicking on the bars of the pyramid and dragging them to where youíd like to set the data. To switch from percentages to numbers, or vice-versa, click in the dark gray area immediately below the graph (on the scale for the x-axis).

To see this graph, if it is not already shown, choose the ìCurrent Age Distributionî command from the Display-type menu. The data can be displayed either as a pyramid graph or as a table.

Displays the calculated population for each time interval. When the population gets large, the population values on the y-axis will be expressed in scientific notation, for example: 5.00 e+ 07 (which represents 5 times 10 to the 7th power, or 50,000,000.

The values displayed are calculated from other population values; you cannot change this graph directly. You may alter the current population size by choosing "Population Size..." from the Settings menu and entering the value that you want in the dialog box.

To see this graph, if it is not already shown, choose the ìPopulation Size vs. Timeî command from the Display-type menu.The data can be displayed either as a graph or as a table.

The graph above shows population size vs. time for two trials.

The age distribution of an exponentially growing population usually converges toward a stable age distribution with time. This graph displays the stable age distribution (males are in pale blue, on the left; females are in pale red, on the right). The values displayed are calculated from the age-specific mortality and fertility values; you cannot change this graph directly.

To see this graph, if it is not already shown, choose the ìStable Age Distributionî command from the Display-type menu. The data can be displayed either as a pyramid graph or as a table.

The Summary Statistics table presents values related to the populationís growth. These composite values are calculated from the values which are entered in other graphs or tables; you cannot change these values directly.

To see the Summary Statistics table if it is not already shown, choose the ìSummary Statisticsî command from the Display-type menu. The table above shows summary statistics for two trials, with the first trial having a shorter doubling time and more rapid rate of growth.

You can select the statistics that will be displayed by choosing "Summary Statistics..." from the Settings menu and checking the appropriate boxes in the "Display Settings" dialog box. The following are the values that can be displayed in this window:

ï Doubling Time: How many years it would take for the population to double, (or halve, if the value is negative; assuming the population has reached a stable age distribution ).

ï Innate Capacity for Increase: A measure of the capacity for the population to grow (or shrink, if negative).

ï Mean Life Expectancy: The average age to which an individual can be expected to survive.

ï Total Fertility Rate: The total number of offspring a female would have, on average, if she were to live to the maximum age.

ï Finite Rate of Increase: A measure of the rate of growth of a population. The amount that the population must be multplied by to give the population size in the next time unit (assuming the population is in stable age distribution).

ï Generation Time: The average age at which a female gives birth to her offspring. This is equivalent to the time that it takes for a population to increase by a factor equal to the Net Reproductive Rate.

ï Net Reproductive Rate (R₀): The average number of offspring an individual in a population will produce in his/her lifetime. Unlike the Total Fertility Rate, R₀ depends on age specific mortality rates.

ï Crude Birth Rate: The number of individuals, per thousand in the population, born during a time interval. For example, crude birth rates for the human population vary from nation to nation, generally falling in the range from 10 per 1000 per year to 40 per 1000 per year.

ï Crude Death Rate: The number of individuals, per thousand in the population, dying during a time interval. For example, crude death rates for the human population generally range from 5 per 1000 per year to 25 per 1000 per year.

ï Percent Juvenile: The fraction of the current population that is below a certain age. The default setting of 15 can be changed by choosing "Model..." from the Settings menu.

ï Dependency Ratio: The fraction of the current population that is "dependent" on the rest of the population. In the human population, this has generally been considered to be the fraction under 15 years plus the fraction over 65 years. The default settings are 15 and 65. You can change this age by choosing "Model Settings... from the Settings menu.

ï Percent Juvenile at the Stable Age Distribution: The fraction of the population that would be below a certain age if the population was at its stable age distribution.

ï Dependency Ratio at the Stable Age Distribution: The percent juvenile plus the fraction over a certain age, if the population were at its stable age distribution.

c