5 ms·

thanks for the explaining why you suggested the world's birth rate is dropping. As you say, population of the earth as a whole is still increasing, and the bir

by hnriot 13y ago

thanks for the explaining why you suggested the world's birth rate is dropping. As you say, population of the earth as a whole is still increasing, and the birth rate is not in decline. It's not a mean vs. median problem at all. If it were in decline we wouldn't be facing one of the biggest global issues of over population.

rdl 13y ago
Population is one number. Birth rate is a derivative of that. A rate of change in birth rate is the second derivative of population. Population'' is clearly negative -- the global birth rate IS in decline, and has been since 1950 according to the UN (I don't see earlier stats). Population is still increasing because Population' is positive. (well, actually Birth rate > death rate). Per country, it actually is a median vs. mean problem; most countries (hence, median) have below-replacement birth rates; there are a limited number of countries with substantially above replacement birth rates, due to both fertility and the demographic composition (lots of young people).
- dragonwriter 13y ago
  > Population is one number. Birth rate is a derivative of that. No, its not. For several reasons. Firstly, because the derivative of population is the rate of population growth (persons/unit time) which is not just the rate of births per unit time, but births minus deaths. Secondly, because "birth rate" isn't the rate of births per unit time, but the rate of births per unit time per unit population. > Population'' -- the global birth rate IS in decline, and has been since 1950 according to the UN Those statements are only distantly related and only the latter is clearly true. While the birth rate (births/person/year) has been dropping for quite a long time, the second derivative of population with respect to time was around 0 from the late 1980s to recently, with the first derivative hovering at around 1 gigaperson / 12 years, though projections are that that rate of increase is slowing somewhat now. The second derivative of population with respect to time was actually positive for most of the 20th century, with each successive billion people added in a shorter period of time until it leveled off around at the 12 years / billion level. [1] http://en.wikipedia.org/wiki/Population_growth http://en.wikipedia.org/wiki/Population_growth

by hnriot 13y ago

rdl 13y ago

Population is one number. Birth rate is a derivative of that. A rate of change in birth rate is the second derivative of population. Population'' is clearly negative -- the global birth rate IS in decline, and has been since 1950 according to the UN (I don't see earlier stats). Population is still increasing because Population' is positive. (well, actually Birth rate > death rate). Per country, it actually is a median vs. mean problem; most countries (hence, median) have below-replacement birth rates; there are a limited number of countries with substantially above replacement birth rates, due to both fertility and the demographic composition (lots of young people).

dragonwriter 13y ago
> Population is one number. Birth rate is a derivative of that. No, its not. For several reasons. Firstly, because the derivative of population is the rate of population growth (persons/unit time) which is not just the rate of births per unit time, but births minus deaths. Secondly, because "birth rate" isn't the rate of births per unit time, but the rate of births per unit time per unit population. > Population'' -- the global birth rate IS in decline, and has been since 1950 according to the UN Those statements are only distantly related and only the latter is clearly true. While the birth rate (births/person/year) has been dropping for quite a long time, the second derivative of population with respect to time was around 0 from the late 1980s to recently, with the first derivative hovering at around 1 gigaperson / 12 years, though projections are that that rate of increase is slowing somewhat now. The second derivative of population with respect to time was actually positive for most of the 20th century, with each successive billion people added in a shorter period of time until it leveled off around at the 12 years / billion level. [1] http://en.wikipedia.org/wiki/Population_growth http://en.wikipedia.org/wiki/Population_growth