Financial Risk - Diversification

Diversification

Financial risk, market risk, and even inflation risk, can at least partially be moderated by forms of diversification.

The returns from different assets are highly unlikely to be perfectly correlated and the correlation may sometimes be negative. For instance, an increase in the price of oil will often favour a company that produces it, but negatively impact the business of a firm such an airline whose variable costs are heavily based upon fuel. However, share prices are driven by many factors, such as the general health of the economy which will increase the correlation and reduce the benefit of diversification. If one constructs a portfolio by including a wide variety of equities, it will tend to exhibit the same risk and return characteristics as the market as a whole, which many investors see as an attractive prospect, so that Index Funds have been developed that invest in equities in proportion to the weighting they have in some well known index such as the FTSE.

However, history shows that even over substantial periods of time there is a wide range of returns that an index fund may experience; so an index fund by itself is not "fully diversified". Greater diversification can be obtained by diversifying across asset classes; for instance a portfolio of many bonds and many equities can be constructed in order to further narrow the dispersion of possible portfolio outcomes.

A key issue in diversification is the correlation between assets, the benefits increasing with lower correlation. However this is not an observable quantity, since the future return on any asset can never be known with complete certainty. This was a serious issue in the Late-2000s recession when assets that had previously had small or even negative correlations suddenly starting moving in the same direction causing severe financial stress to market participants who had believed that their diversification would protect them against any plausible market conditions, including funds that had been explicitly set up to avoid being affected in this way

Diversification has costs. Correlations must be identified and understood, and since they are not constant it may be necessary to rebalance the portfolio which incurs transaction costs due to buying and selling assets. There is also the risk that as an investor or fund manager diversifies their ability to monitor and understand the assets may decline leading to the possibility of losses due to poor decisions or unforeseen correlations.