The world population increases at the rate of one to two percent per year. This gradual rate of increase means that a real time clock of world population looks the same on a computer screen whether the equation is exponential or linear. The increase of population on December 31 is faster than it was on January 1. But at one or two percent growth, the end of the year looks like the beginning of the year on the screen.
The popclk program was designed as a general purpose clock of any type of increase or decrease, including economic data like national debt. The average rate of increase or decrease is the most general way to calculate a real time clock. This assumes that the first and second derivatives of growth are fairly flat. If you want to adapt an exponential equation to the clock, you are welcome to recalculate the dbltkdlta field in the program during each cycle in the count function.
popclk 72898133
In this example, 72898133 is the annual increase in world population from July, 2003 to the projected population in July, 2004.
Here's an example showing popclk used for the national debt.
popclk 500000000000 'National Debt'
The second parameter is the title on the screen.
Press h or the space bar for online help.
Press t to toggle the time mode.
The time modes are:
Press r to reset the population count and the relative time.
Press n to change the annual rate of increase or decrease.
Press c to change the caption.
Press Escape or q to quit.
popclk shows the total change in population from the time the program starts running.
The display window is designed to be small, so that you can place the window in a corner while you work on another task.
popclk calls nanosleep during each cycle, to keep the load to a minimum.
The X Windows version of popclk uses the same formulae as the text version of the program. Only the input and output have changed. And the program is called xpopclk.
The population model that accompanies popclk allows you to examine a few factors in human population that result in the totals published by the U.S. Bureau of the Census.
For instance, the model allows you to make tradeoffs between life expectancy, the total number of children per female, the fertility period of the female, the mortality rates during different stages of life, the mortality rate of the mother during childbirth, and the rate at which old age accelerates.
World POPClock Projection
U.S. Bureau of the Census.
Total Midyear Population for the World: 1950-2050
U.S. Bureau of the Census.