THE GLOSSARY · MARKETS
Variance
Your results swing naturally around their average. A bad year does not prove your method is broken — and a good year does not prove it works.
By the Yoseri News desk · · 1 min read
You look at this year’s return and wonder whether your strategy holds up. Variance is exactly that: the gap between what a strategy gives you over a short period and what it gives you on average over a long one.
That is why one year of return teaches you almost nothing. A portfolio whose expected real return is 5% a year will go through years at −15% and years at +22%. Both are normal. Neither is a signal.
What follows is counter-intuitive: the shorter your horizon, the more chance decides; the longer it is, the more the average comes through. That is why a thirty-year retirement projection is more reliable — as an order of magnitude — than a twelve-month forecast.
This holds for your own decisions, not just your investments. Judging your savings rule on two months makes no sense. Two months under the rule out of twelve, both tied to a drop in income, describe an ordinary year — not a failure.
In Yoseri, the Savings and goals page shows you what pauses and what carries on when an income stops. Your two months under the rule read there as a sequence, not as a fault.
Where the figures come from
The maths in this article starts from the assumptions written above. Run them again with your own figures — you should land on the same numbers.
Yoseri News is an educational publication. Nothing in this article is investment advice, a recommendation to buy or sell, or tax advice. Yoseri is registered as neither an adviser nor a dealer with any market authority.