The main types of risk
Market risk (systematic risk): the risk from overall market movements that affect all investments simultaneously — economic recessions, interest rate changes, geopolitical events. Diversification cannot eliminate market risk; it is the unavoidable price of participating in financial markets. Credit (default) risk: the risk that a borrower (company or government) fails to make interest or principal payments. Relevant for bonds and any lending instrument. Inflation risk: the risk that investment returns are outpaced by inflation, eroding purchasing power even when nominal returns are positive. Cash savings face significant inflation risk. Liquidity risk: the risk that you cannot exit an investment quickly without significant price impact — relevant for property, private equity, and small-cap stocks. Concentration risk: the risk of losses from having too large a proportion in a single asset, sector, or geography.
Systematic vs unsystematic risk
A key distinction in finance is between systematic risk (market risk that cannot be diversified away) and unsystematic risk (company-specific or sector-specific risk that can be reduced by diversifying). If you hold only one stock, you bear both types of risk. If you hold 50 uncorrelated stocks, unsystematic risk diversifies toward zero — your portfolio’s risk approaches just the systematic component. This is why diversification is the most fundamental tool in risk management: it eliminates the risks you are not paid to bear (company-specific) while leaving the risks you are compensated for (market risk). Holding a single stock in the hope of higher returns is bearing concentration risk without compensation — a bet, not an investment.
What this means for you
Assess your portfolio against each risk type explicitly. For most investors, the biggest overlooked risk is inflation risk on cash savings — it is invisible in the short term but devastating over decades. The second most overlooked is concentration risk: holding mostly UK equities in a UK-based account, earning a GBP salary, owning a UK property, and saving in a UK pension concentrates extraordinary amounts of UK-specific risk. A global equity index fund is one of the simplest tools for managing concentration risk across geographies and sectors simultaneously. Risk cannot be eliminated — only redistributed. Choosing which risks to bear deliberately is the foundation of sensible investing.