Risk–return spectrum

The risk–return spectrum (also called the risk–return tradeoff or risk–reward) is the relationship between the amount of return gained on an investment and the amount of risk undertaken in that investment. The more return sought, the more risk that must be undertaken.

There are various classes of possible investments, each with their own positions on the overall risk-return spectrum. The general progression is: short-term debt; long-term debt; property; high-yield debt; equity. There is considerable overlap of the ranges for each investment class.

All this can be visualised by plotting expected return on the vertical axis against risk (represented by standard deviation upon that expected return) on the horizontal axis. This line starts at the risk-free rate and rises as risk rises. The line will tend to be straight, and will be straight at equilibrium - see discussion below on domination.

For any particular investment type, the line drawn from the risk-free rate on the vertical axis to the risk-return point for that investment has a slope called the Sharpe ratio.

On the lowest end is short-dated loans to government and government-guaranteed entities (usually semi-independent government departments). The lowest of all is the risk-free rate of return. The risk-free rate has zero risk (most modern major governments will inflate and monetise their debts rather than default upon them), but the return is positive because there is still both the time-preference and inflation premium components of minimum expected rates of return that must be met or exceeded if the funding is to be forthcoming from providers. The risk-free rate is commonly approximated by the return paid upon 30-day or their equivalent, but in reality that rate has more to do with the monetary policy of that country's central bank than the market supply conditions for credit.

The next types of investment is longer-term loans to government, such as 3-year bonds. The range width is larger, and follows the influence of increasing risk premium required as the maturity of that debt grows longer. Nevertheless, because it is debt of good government the highest end of the range is still comparatively low compared to the ranges of other investment types discussed below.

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