Value at risk (VAR)

VAR attempts to assess the odds of losing money on a portfolio of, say, shares. There are three key inputs.

First, a confidence level nothing about the future is ever known with absolute certainty, but VAR tries to offer 95% or even 99% confidence. Next, there's a time period this could be a day, week or month. Finally, there's an estimated worst-case loss.

The actual calculation is complex and can be done several different ways. But the conclusion is typically similar, for example, "I am 99% confident that if I invest $1m now I will not lose more than 7% of it by the end of the day".

Subscribe to MoneyWeek

Subscribe to MoneyWeek today and get your first six magazine issues absolutely FREE

Get 6 issues free

Sign up to Money Morning

Don't miss the latest investment and personal finances news, market analysis, plus money-saving tips with our free twice-daily newsletter

Don't miss the latest investment and personal finances news, market analysis, plus money-saving tips with our free twice-daily newsletter

Sign up

Sadly, there is always a small chance of a random 'black swan' event occurring (such as a stockmarket crash). If your VAR model fails to build that in, you could end up losing a lot more.