Everybody’s Blogging

Tim Bray reports that, by Dave Sifry's numbers,

the number of known blogs, now somewhere around 25 million, has been doubling every 5½ months. Which calls for a quickie Perl script... aha: At this rate, in August 2009, the number of known blogs will more or less equal the population of the world.

And he links to wikipedia saying that the world population was recently 6.5 billion and will be about 6.8 billion in 2010. Okay, but why a Perl script? I'd rather just say

blogs(now)=25E6
WorldPop=6.5E9
b(m)=blogs(now+m)=blogs(now)*2^(m/5.5)
ln(b(m)) = ln(25E6)+(m/5.5)*ln(2)
( ln(6.5E9)-ln(25E6) )* 5.5/ln(2) = m

and therefore we want to ask Google

((ln(6.5E9) - ln(25E6)) * 5.5) / ln(2) = 44.123023

That's 44 months from February 2006, which is indeed in 2009 though I doubt August. Hmm...would it be better to loop through months in Javascript, figuring that a 5.5 doubling time implies about a 70/5.5% interest rate per month? That would be:

javascript:{var i=0;for(var n=25E6;n<6.5E9;i++)n*=(1+.70/5.5);alert(i);}

47 months; not as close as I thought, but not far off. Unless I'm wrong as usual.