Volatility
How sharply an investment's value swings up and down over short periods.
Volatility measures the size and frequency of price movements. Shares are volatile; cash is not. Higher volatility generally accompanies higher expected long-term returns.
It is often equated with risk, but the two differ. Volatility is the discomfort of watching values move; genuine risk is permanently losing capital or being forced to sell at the bottom.
For a long-term investor, volatility is the price of admission for higher returns rather than a danger in itself. It only becomes a real loss when it triggers a decision to sell.
Time horizon changes what volatility means. Over a single year share returns vary enormously, but over twenty-year periods the range of outcomes narrows considerably, which is why the same asset can be reckless for one investor and appropriate for another.
The same fall, two outcomes
A 30% market fall costs nothing to an investor who holds until recovery. The same fall permanently destroys capital for someone who sells at the bottom.
The bit people get wrong
The most damaging response to volatility is switching to cash after a fall. It converts a paper decline into a realised loss and reliably misses the sharpest days of the recovery.
Common questions
How much volatility should I accept?
As much as your time horizon allows and your temperament can tolerate without selling. An allocation you abandon in a downturn was too aggressive regardless of the theory.
Are defensive assets volatility-free?
No. Bonds move with interest rates and can lose value, though typically far less than shares. Only cash is genuinely stable in nominal terms.
Does volatility mean a bad investment?
Not at all. Shares have been the most volatile mainstream asset class and also among the best performing over long periods.