This TED Talk features cognitive and computer scientist Tom Griffiths, recorded live at TEDx Sydney, 2017.

If there's one city in the world where it's hard to find a place to buy or rent, it's Sydney.

And if you've tried to find a home here recently, you're familiar with the problem.

Every time you walk into an open house, you get some information about what's out there and what's on the market.

But every time you walk out, you're running the risk of the very best place passing you by.

So how do you know when to switch from looking to being ready to make an offer?

This is such a cruel and familiar problem

that it might come as a surprise that it has a simple solution.

37%.

If you want to maximize the probability

that you find the very best place,

you should look at 37% of what's on the market

and then make an offer on the next place you see which is better than anything that you've seen so far. Or, if you're looking at 37% of what's on the market, and then make an offer on the next place you see

which is better than anything that you've seen so far.

Or, if you're looking for a month,

take 37% of that time,

11 days, to set a standard,

and then you're ready to act.

We know this because trying to find a place to live

is an example of an optimal stopping problem,

a class of problems that has been studied extensively by mathematicians and computer scientists.

I'm a computational cognitive scientist.

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