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Comment by jstanley | Hacker News Reader

> Data tells the story: on average, if you sell your home within 90 days, you’ll do it at 15% higher than what you bought it for.

There's some selection bias here. Those who got lucky (e.g. they bought the house cheaply) found it easy to sell for a good price quickly. Those who got unlucky and couldn't find a buyer quickly are excluded from the "90 days" window so don't contribute to the statistic.

It might be true that homes sold within 90 days of purchase sold for an average of 15% higher than the purchase price, but it doesn't mean you can expect to sell a home within 90 days of purchasing it for 15% more than you paid.

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If you haven’t sold in 90 days, your price is to high. There is always a buyer at the right price.

As a real estate investor, I specially target homes going unsold after long durations on the market due to unrealistic expectations.

> If you haven’t sold in 90 days, your price is to high

Right. So it's selection bias. The people who can get a price 15% more than they paid manage to sell within 90 days, the people who can't dont.

That’s not selection bias, that’s a functioning marketplace. Something is worth what someone will pay for it. If demand is increasing, prices increase.

There is clearly selection bias in the quoted figure of houses sold within 90 days, because people try to maximise what they'll get.

People only tend to drop the price after it's been sat around for a while. By definition, such sales are not very likely to happen within the 90 day window and therefore do not contribute to this average.

What window of time would provide better data if not 90 days? 3 months? 6 months? A year? Anything more than 90 days and it’s stale market data.

There's selection bias at any time scale. Those who manage to sell their property at all are getting better prices than those who fail to do so.

The point is that you can't calculate a probability of making +15% within 90 days just by looking at how many of the houses sold within 90 days were sold for +15%. Or any +X%. Or any time period.

If you really want to calculate such a probability, you need to buy a bunch of houses at random, then try to sell them, and then see how much you made and how long it took. The data used in the post is not suitable.

The point that the op is making is that this is only looking at the "successful" trades. It is not looking at the set of "attempted" trades. So it is only looking a selection of the possible trades, and so there is a selection bias involved in the data set. This is very much a form of survivor bias.

It is likely that it also "only" includes those that managed to buy a house at under market rates, and sold at, or above, market rates within 90 days. Anyone who is buying to live in is likely paying as much or more as the "sale" price.

This is further stated in the market, since the annualised rate of return is 650%, but house prices are _not_ going up that quickly.

Which, in turn, means that distressed buyers are not necessarily going to see a 15% increase in the price of their house in 90 days, nor are they going to see a ~30% in 180 days, since their property may not be "undervalued".

Attempted transactions do not make a market. Completed transactions do.

Exactly

No one is saying the market is wrong or the data is wrong. Just that the implications the author makes based on the data are unjustified.

Sure. But the right (market) price 30 days later might be the same price you bought it at (or less), meaning you'll be selling it at a loss after various transaction fees.

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