What is... index-linking
What is...
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Index-linking can protect investments against inflation. But what are the pros and cons?
Inflation eats away at the value of money over time: €100 in 2020 will not buy the same basket of goods and services it buys now. To counter this, investments can include measures to take account of inflation.

This is known as index-linking. As the name suggests, the index-linked investment payout – interest on an account or bond, or return on an investment – is linked to a particular index. Such arrangements can apply for a wide range of common investments, including savings accounts, bonds and pensions.

Inflation fighting
A common form of index-linking is to ensure investment income increases at the same rate as inflation. A savings certificate, for example, might pay 1% a year plus an extra amount to match the speed at which inflation has gone up. This aims to ensure that the purchasing power of the investment does not deteriorate as prices rise. The eZonomics video How to protect your savings from inflation explains further.

Arguments for and against index-linking
Because of the inflation-related payments, index-linked investments typically have a basic rate of interest that is lower than that on an ordinary investment. When choosing between an index-linked account and an ordinary account for which payments are not linked to inflation, investors weigh up how fast they think inflation is likely to rise and how much risk they want to take. A bond offering 5% interest might look better than a “linker” paying 1% plus inflation. But if inflation rises by more than 4% a year, the index-linked bond will pay more. If the inflation rate slows or turns negative, then linked bonds do worse.

Pensions policy
Retirees buying a pension annuity have the option to index-link the payments so their future income rises with inflation. However, as this tends to mean a lower starting income, it's not an easy decision. A standard annuity will pay a fixed amount, say €5,000 a year, whose purchasing power will decline over time. An index-linked payment might pay €3,000 a year but the amount increases inline with inflation. A pensioner has to decide whether the index-linked payments will “catch up” with the alternative. That will depend on how fast inflation rises and how long they live. Likewise, home insurance policies can index-link the value of the goods insured to the rate of inflation.

Your index or mine? 
Much of investors’ decision making on index-linked investments will likely depend on which index the payouts are linked to. Most people understand that inflation is a general rise in prices of goods and service, with an eZonomics guide describing inflation in further detail. 
But inflation can be measured in different ways.
While the United States and most European countries use a consumer prices index, the United Kingdom also currently uses a retail prices index as a link for certain government bonds, pensions and benefits. As well as inflation, investments can be linked to stock market indices to ensure they match average gains in equity prices.
These accounts increase your savings by the amounts by which the linked index rises. But if the equity index goes down, you may lose money. It can be important to study carefully the details of index-linked investments and the details of the particular index used to calculate returns.

By Phil Thornton
Clarity Economics’ lead consultant
What is... is an occasional series that explains important ideas and terms.