the comment in the article about instances of melanoma increasing at a rate of 6% annually begs the question ‘how does that compare with population increase?’ i believe the answer is roughly 1.25%. it doesn’t defeat the impact of the melanoma statistic, but it is necessary to give it some meaning.
btw, the link for that population growth statistic is:
http://www.census.gov/ipc/www/img/worldgr.gif
While Cecil’s article uses anbiguous wording, the Mother Jones article clearly states “More studies prove this link, melanoma rates are rising about 6 percent each year, and sunscreen sales are continuing to climb.” So population is irrelevant.
Come to think of it, what’s with the chart you gave? The title is “World Population Growth Rate: 1950-2050”, but at the bottom it says that the source is the US Census Bureau. As far as I know, the US Cenusus Bureau keeps track of only US population, and only in decade-long increments, rather than the much smaller ones shown in the graph. And the Bureau certainly doesn’t have any data from 2050.
population is relevant because if there’s 1 case of melanoma among 10 people this year and next year there’s 2 cases, you might say - hey, what’s the deal - melanoma increased 100%! but if i told you that the population also increased 100% to 20 people, it would mean that melanoma continues to affect only 10% of the population. all people related numbers can be expected to rise as long as the population grows. percentages are only relevant with respect to population growth percentages. so if the melanoma percent rise (cases - not ratio of cases to people) was less than the population percent rise, then you might assume that sunscreen or some other factor was having a positive effect on reducing melanoma.
as for the chart link, i just found it from searching on the web. and while the census bureau keeps track of us population, i’m sure with a little research they could put together a chart of world population - i mean, they’re already in the population tracking business, so why not? i figured the future stats were just forecasts based on historical data.
zwaldd - Your point is well taken, and statisticians are known to make mistakes, but generally it is understood that when someone makes a statement of the kind “melanoma rates are rising about 6 percent each year” the meaning is that the number of cases for, say, ten thousand people, has increased by 6%.
thanks - i actually posted my confusion about percent per capita statistics in gq and they set me straight.
zwaldd, I think in this case the relevant term is
So while the percent increase is not a per capita term directly, the rate of melanoma incidents is a per capita term.