There are currently somewhere in the range of 308,698,000 (three hundred and eight million, six hundred ninety eight thousand) people in the United States of America. The world's population is closer to 6,803,188,000 (six billion, eight hundred and three million, one hundred eighty eight thousand.) Using those numbers, the population of the United States makes up only about four and a half percent of the world's total population.
The main way these numbers are tracked is through censuses and birth and death records. In more developed countries, these numbers are relatively accurate, though the census is taken only every few years. Births and deaths are generally well-tracked in these places, however, so a general idea of how many people are in these countries is somewhat easy to find. In less developed places, however, the numbers are much more amorphous and less reliable, because many people are out of the range of such census taking, and most births and deaths go entirely unrecorded other than by family members.
Population trends are then used to extrapolate the population of these places and the earth itself over time. While the numbers certainly are not ever accurate down to the person, they give a good baseline number from which to understand the size of the world's human population.
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Posted 5129 day ago