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by Valentino Piana (2002)



1. Significance
2. Rates types
3. Determinants
4. Impact on other variables
5. Long-term trends
6. Business cycle behaviour
7. Data
8. Formal models
9. Links




The interest rate is the profit over time due to financial instruments.

In a loan structure whatsoever, the interest rate is the difference (in percentage) between money paid back and money got earlier, keeping into account the amount of time that elapsed. If you were given 100$ and you give back 120$ after a year, the interest rate you paid was 20% a year.

Nominal interest rate are laid down in contracts between involved parties. Real interest rates somehow adjust the nominal ones to keep inflation into account. For instance if inflation was 15%, in the previous example the real interest rate can be said to be 20%-15% = 5%, in a simplified way of computation.

Interest rate paid in actual transactions should not be mistaken for the subjective inner computational tool expressing patience or impatience and the balance between present and future flows, which is called "discount rate" in investment decisions, which in turn can be influenced by the cost of capital, both internal and external, but remains rooted in the actor's identity, history, and interpretation of business cycle and long-term trends.

Rates types

There exist several nominal interest rates, depending on the following elements:

1. the institution offering the credit;
2. the organization receiving the loan, which can be more or less trustworthy;
3. the funds' use and the aims of the financed plan (consumption, investment, working capital,...);
4. the time length of the loan with the broad difference between short-term interest rate and long-term interest rate;
5. the ex-ante flexibility of the contract with the alternative between a fixed interest rate or a variable interest rate;
6. the number, the frequency and the amounts of reinbursement actions;
7. the conditions under which the loan is agreed, for example regarding guarantees and collateral;
8. the presence or absence of a market for converting loan conditions and for changing the parties involved in the contract.

For instance, the fixed interest rate paid to a bank by private firms for financing an industrial investment, characterized by a payback period of 3-7 years, exerts a crucial importance in the economy. In fact, it may influence overall investment, thus the business cycle.

As the typical lending institution, the bank finances its credit activity in several ways:

1. by collecting money from households deposits (and pay to them an interest rate on deposits),

2. by issuing its own obligations, characterised by a bonds interest rate,

3. by taking short-term loans from other banks, paying the interbanking interest rate,

4. by borrowing money from the central bank, which requires an interest rate for refinancing operations.

When establishing the interest rate to the public, banks all over the world make reference to these rates (e.g. "1.5% more than EURIBOR" - the famous interbank interest rate for loans in euros).

If the firm is a sound primary firm with excellent trustworthiness, the bank would agree an interest rate only slightly higher than the rate the same bank would be requested to pay in the interbanking market from other lending institutions. By contrast, for smaller industrial firms, the rate usually would be significantly higher because of the worsened credit risk.

Apart from bank loans, a key interest rate in the economy is that paid on Treasury bonds. Similarly, private, public and state-owned firms issue bonds as well, expressing further nominal interest rates.

Both state and firm bonds can be continously exchanged in public markets, making their effective interest rate dependent on the price at which it has been bought. A bond, whose nominal price is 100 and interest rate is 5%, will in reality give a 10% yield if it is bought at a price of 50 in the public market.

Households receive interests on their bank accounts, usually higher if they block money for a certain period (savings account) and lower if it is an "a vista" account (current account).

Conversely, households pay an interest when taking loans for consumption purposes.

The following picture summarizes most of what we said, with an arrow for each kind of interest rate:



Many other interest rates could be found on the light of the fact that any negotiation can produce a specific rate.

In term of comparison among their mutual relationships, in some cases it is known which rate is higher and which is lower but differences (the so-called "spread" between two rates) can widely vary over time and among countries.

Which is the leading interest rate, in parallel to which all the others move? Does it exist such an interest rate? Well, in some analysis it may be easier to consider just one interest rate, but in reality there is no guarantee that all the others will move exactly in parallel.

Still, the IS-LM model makes usually reference to one interest rate, influenced by the central bank and having an impact on investment.


Changes in interest rates structure depend on reasons that are both internal and external to financial markets:

1. Different types of interest rate are linked and influence each others, so that the functioning of the financial markets and their international relationships explain a good deal of interest rate fluctuations.

2. Economic performance, perspective and expectations of potential loan receivers as well as in the overall economy play an important role.

To keep things easy, we could say that interest rates are determined in negotiations, which are more or less public, binding a larger or narrower number of contrahents, more or less depending on publicly available benchmark rates.

In a sentence, interest rates are set within institutional agreements.

Central bank policy is one of the most powerful factor impacting on these agreements, for example through the instrument of direct determination of official discount rate or the rate for refinancing operations.

An increase of money offered in the interbank market by the central bank is conducive to a fall in the interbank rate, upon which many contracts are based.

To the extent the Ministry of Treasury influences the interest rates on its own bonds, it provides an important reference point for the economy.

Since for many banks the risky commercial loans to firms are alternative to safe Treasury bonds, there are paradoxically situations in which the interest rate policy in the hands of the Treasury not less than of the central bank.

International tendencies exert an important influence on domestic conditions as well, since financial markets are now global in scope and there is a growing co-operation among central banks.

Still, domestic commercial bank policies say the last words on loan agreements and conditions.

In general, an increase of interest rates may be provoked by the following factors alternatively or cumulatively:
1. an anti-inflationary policy of the central bank, based on restrictions to the growth of the nominal money supply and on rising discount interest rate;
2. a policy by the central bank aimed at revaluating the currency or defending it from devaluation,
3. the attempt of the Treasure of covering public deficit by issuing more bonds in an unwilling market,
4. an attempt of banks of widening their margins, possibly as a reaction to losses,
5. any increase in other interest rates, also foreign rates arisen for whatsoever reason.

By contrast, a fall in interest rates may be justified especially by the following reasons:
1. an expansionary policy of the central bank,
2. the requests of industrialists and trade unions for cheaper money in front of a crisis,
3. a loose monetary policy due to a commitment to a fast export-led growth;
4. the end of an inflationary phase;
5. the relaxation of the need for defending the exchange rate, for example thanks to a new monetary union.

Impact on other variables

The traditional effects on an increase of interest rates are, among others, the following:
1. a fall in stock exchange and in the value of other assets (as private and Treasury bonds or houses and real estate);
2. a fall in profitability of firms;
3. a fall in private investment;
4. a fall in consumption credit;
5. an inflow of foreign capital for buying bonds;
6. an upward pressure on exchange rate;
7. a larger public expenditure to pay for a previously cumulated public debt, whose burden might lead to reduction in other chapters in public expenditure;
8. a narrower disposable income for households having a large debt taken at variable rates;
9. a larger disposable income for households that have lent to others at variable rates (e.g. they own government bonds with variable rates);
10. a redistribution of income from debtors to lenders (in the part of debt that has variable rates).

If the rate is kept higher for a longer period of time, also newly agreed fixed rate instruments will adjust up.

Still, the general environment in which the rise takes place is crucial, since such effects can be completely absorbed by other (more powerful) forces. A booming economy might absorbe a small increase in the interest rates possibly well.

Similarly, a non-linear relationship could be worth considering between the size of rate increase and the differentiated effects on real and financial markets.

In fact, a small change in the official discount rate might arguably have no real effect at all, while triggering substantial echos on financial markets.

By contrast, a large and abrupt increase in general interest rates can have devasting effects on crucial real variables, exerting a depressing pressure on GDP and the economy at large. In particular, if prices in the real estate (including housing) market and Treasury bonds are falling, their value as collateral for loans would be reduced. The credit crunch would squeeze private investment. If the business environment is such that the State begins to delay due payments to firms and has difficulties in re-finacing its debt (with some risk of default, even if just in long term perspective) banks might be compelled to reduce credit for current business transactions across the supply chain.

A chain of bankruptcies would close down plants, select the surviving firms, and reduce employment. At the local scale, entire neighbourhoods and towns would economically collapse, with empty buildings and dismissed industrial estate, looking for a future urban regeneration.

The effects will be spread unevenly across industries, with some being much more vulnerable. For instance, there is a strong relationship between interest rates and real estate growth or fall, since all sides of the housing and non-residential market usually leverage debt (the purchaser but also the producer of the new real estate). Many sales are inter-linked, with a purchase made by owners that are able to sell their asset and add only the difference (or extract it, depending on the difference in prices between the two sales), which further contributes to the high sensitivity of the sector to interest rates.

Long-term trends

Interest rates fluctuate over time with an historical ceiling, i.e. a maximum level. Even though in high-inflation periods the nominal interest rate can reach extremely high levels, for long decades a ceiling of 10% is a rule for many countries.

Nominal interest rates have a minimum floor of zero, with the exception of central bank interest rate for refinancing operations which can be negative as a part of monetary policies aimed to stimulate the economy.

Business cycle behaviour

Interest rates primarily depend on policy and expectations, thus the relationships with the business cycle depend on explicit decisions and subjective judgements of key players.

If the interest rates are mainly used to fine tune the business cycle, then they will fall in recessions, slightly but steadily rise with recovery and, finally, will be increased at the end of the growth period to brake possible inflationary dynamics. Soft landing will be targeted, even though hard landing with a recession is an equally likely outcome. In this case, interest rates are pro-cyclical, with usually short-run interest rate being more markedly pro-cyclical than long-term rates.

But other policy rules would imply different behaviour. For instance, if the target is mainly inflation, during a stagflation period (a depressed GDP with high inflation) the interest rates may be particularly high, thus a counter-cyclical pattern would emerge.


Long-term interest rates in Euro countries (2001-2011)

Monthly data for interest rates (1980-2011) in 6 major countries

Government bonds and other rates in 14 countries (2007-2011)

Lending interests rates in 184 countries (1960-2010)

Lending and deposit interest rates in 13 EU countries (1980-2001)

Long-term interest rates in OECD countries (1982-1998)

Data for all the variables in IS-LM model

Race and gender discrimination in lending rates to business owners

EU data for all the variables in IS-LM model (Germany, France, Italy, Spain, UK, Switzerland and other 13 European countries)

To see the long term growth impact of nominal interest rate policy, use together the abovementioned data with the time series of GDP and of the other main macroeconomic indicators

Savings behaviors in the UK population

Long-term interest rates in globalized markets

Formal models

An interactive map of how the economy works according to a basic macroeconomic scheme: the IS-LM model

Is the interest rate relevant for R&D and advertising investment? Find out your own answer by playing to "Race to market"

Interest rate, bancruptcy and heterogeneous firms: new ingredients for explaining business fluctuations


Recent monthly US interest rates



Key concepts