Fermi problem: weddings

http://lesswrong.com/lw/h5e/fermi_estimates/

How much money is spent on weddings in the US? I figure US cohorts are 4 million people per year. Assuming almost everyone gets married eventually, and that those who don't are made up for by re-married people, that's 4 million weddings a year. Guessing $10k per wedding, $40 billion.

==Data==

A couple sources said $40 billion or $51 billion, and I felt very proud -- getting within a factor of 10 is a decent success for a Fermi problem, never mind a direct hit -- until I realized that weddings involve two people, so I should have figured 2 million weddings, and $20 billion. Oops! (In my defense, it was like 3am.)

The actual numbers quoted seem rather scattered, actually. Wikipedia says 2.5 million weddings and $40 billion, yielding $16,000/wedding, but the cited source no longer exists. Citing a different source it says $28,400 per wedding, but at 2.5 million that should give a total of $71 billion.

This says 2.1 million, spending a total of $86 billion, or $41,000 per wedding. It also claims $70,000 per wedding in Japan in 2005. Given that most sources have Japan GDP/capita at a fair bit less than the US -- especially in PPP -- I am skeptical of this source.

And this says "* The average wedding cost is $26,501, slightly more than a 5% decrease from 2009 when the average cost was $28,082 but up $8,000 since 2002." without giving total numbers.

(Going from $18,000 in 2002 to $26,000 in 2011 seems like a huge jump. 44% increase. Well, there is inflation... but 2% inflation over ten years gives 22%. 3%, 34%. 4%, 48%. But inflation's been low, at least since 2008...)

Business Week cites $51 billion, which would be $24,000 for 2.1m weddings or $26,000 for 2m weddings.

===

So, I thought this would be a trivial problem, where we Fermi something we can simply look up as an exercise and calibration of estimation, but actually we've got a scatter of numbers and estimation may help us trust some sources more than others. 2 million and about $25,000 seem the most likely numbers, for $50 billion; whether the $25,000 is a *typical* number or is badly inflated by big spending of the rich, or even inflated by selective reporting, is unclear. Example of the latter: does anyone have any real idea how much is spent on weddings, or is it 'couples who register with us spend an average of $25k, so we extrapolate from there, even though courthouse elopements are invisible to us?'

Will Oremus in fact says it's the latter:

One of the most extensive surveys, and perhaps the most widely cited, is the “Real Weddings Study” conducted each year by TheKnot.com and WeddingChannel.com. (It’s the sole source for the Reuters and CNN Money stories, among others.) They survey some 20,000 brides per annum, an impressive figure. But all of them are drawn from the sites’ own online membership, surely a more gung-ho group than the brides who don’t sign up for wedding websites, let alone those who lack regular Internet access. Similarly, Brides magazine’s “American Wedding Study” draws solely from that glossy Condé Nast publication’s subscribers and website visitors. So before they do a single calculation, the big wedding studies have excluded the poorest and the most low-key couples from their samples.

In 2012, when the average wedding cost was $27,427, the median was $18,086. In 2011, when the average was $27,021, the median was $16,886. In Manhattan, where the widely reported average is $76,687, the median is $55,104. And in Alaska, where the average is $15,504, the median is a mere $8,440. In all cases, the proportion of couples who spent the “average” or more was actually a minority. And remember, we’re still talking only about the subset of couples who sign up for wedding websites and respond to their online surveys. The actual median is probably even lower.

So who knows? My $10,000 per typical wedding and $20 billion total might not be so far off.