Chris has a master's degree in history and teaches at the University of Northern Colorado.
We need to figure out how many people are in our community. Why? Pick a reason! We've got potholes to fix, and we need to know how many taxpayers there are. We're going to have to pay for public schools, and we need to predict the number of children. We've got to stock health clinics, post offices, and government offices with enough people and supplies to meet the public's needs.
I mean, what if we run out of marriage licenses or bandages or stamps or cafeteria lunches? We'd have an uprising on our hands! So we need to know a lot of information about this community, and for that we turn to demographics, the statistical analysis of a population. And then we can get to work fixing all those problems.
The Demographic Balancing Equation
Demographics can tell us a lot of information, but counting every single member of the population takes a lot of work. Really, the government only does this once every ten years with the national census, the most thorough demographical record of a nation. This counts as much as it can, but in between those ten years, it's still important to know how many people you're dealing with.
So rather than re-count every person every year, we simply turn to the demographic balancing equation which calculates population change from year to year. The equation itself is actually pretty simple: total population +/- natural increase +/- net migration = balanced population. See, simple - except that there are a few terms in here that we probably should define!
One of the things we need to know in order to calculate the demographic balancing equation is natural increase, or the population change from births and deaths. Calculating this is pretty easy - just subtract the number of deaths from number of births; that's how much your population increased or decreased from natural causes.
We can get this information without having to ask every person if they've had any births or deaths in the family because these are vital statistics, those statistics that only need to be recorded once through legal documents like birth and death certificates. Those are already on record, so getting that information is a lot easier that conducting a census. So are we ready to calculate the demographic balancing equation? Well, hold your horses, 'cause there's still one more term to figure out.
As anyone living in the United States should realize, people enter this country in more ways than just birth and leave in other ways besides death. After all, what kind of melting pot would we be without all the world's peoples? Net migration counts the total number of immigrants who enter an area and emigrants who leave. So the formula is just immigrants minus emigrants, and there's your population change from unnatural causes. Not unnatural; immigration isn't unnatural, non-natural causes. There we go! And now, we are ready to calculate that equation.
Calculating the Demographic Balancing Equation
All right, so let's see that equation again: total population +/- natural increase +/- net migration = balanced population. Now that we know what those terms mean, we can also expand it to look like this: total population + (births - deaths) + (immigrants - emigrants) = balanced population. Pretty cool, right? Now, technically, this equation can be used on almost any scale, from a small town to an entire hemisphere. But we can't use it to balance the world population because there are no emigrants or immigrants leaving or entering Earth. At least, I don't think so. Anyway, to balance the world population, you just adjust for natural increase. That's it!
All right, are you ready to balance the population of our fictional internet town so we can provide enough fictional internet bandages and fictional internet stamps to our people? Let's say we started with a population of 10,250: 24 people died, 103 were born, 130 emigrated, and 172 immigrated. Now, where's that put us? Just plug the numbers in, and, let's see, carry the one, uh-huh, uh-huh, there we go - our balanced population is 10,371. Wow, we're going to need a lot of stamps. All right, let's get on that! We've got our demographics balanced, and now it's time to start fixing all those problems.
The demographic balancing equation is a formula for determining total population change from year to year. The formula itself is pretty basic: total population +/- natural increase +/- net migration = balanced population. That's it! Natural increase is the number of births minus the number of deaths, and net migration is simply the number of immigrants minus the number of emigrants. If we want to, we can expand the formula to show these definitions, which makes it total population + (births - deaths) + (immigrants - emigrants) = balanced population. And with that, we've balanced our population, and we know how many people are currently in our community. And we'll be sure to have bandages and stamps for each of them.
- Demographics: the statistical analysis of a population
- National census: the most thorough demographical record of a nation
- Demographic balancing equation: equation that calculates population change from year to year; total population +/- natural increase +/- net migration = balanced population
- Natural increase: the population change from births and deaths
- Vital statistics: statistics that only need to be recorded once through legal documents like birth and death certificates
- Net migration: the total number of immigrants who enter an area and emigrants who leave
As you gain knowledge about the demographic balancing equation, you'll increase your ability to utilize the demographic balancing equation to determine the total population change of a given area from year to year.
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