Interest rates
Real and money rate/nominal rate
These ideas come up often in finance, so it’s worth getting the basics clear early.
Nominal rate of interest
The nominal (money) interest rate is the stated interest rate you see quoted by banks and lenders. It includes the effect of inflation.
Real rate of interest
The real interest rate is the interest rate after removing the effect of inflation. It reflects the change in purchasing power.
How do you calculate the real rate when given the nominal rate of interest?
You use the relationship between the nominal rate and inflation.
Real interest rate formula
Where:
- = money (nominal) rate of interest
- = inflation rate
This formula gives you the real interest factor. To get the real interest rate, you subtract from the factor.
If the question asks you to calculate the money rate of interest when the real interest rate is given, use the same relationship and rearrange as needed.
Example 3
KTA has a money (nominal) interest rate of from the bank on an annual basis. The annual inflation rate is . What is the real interest rate that KTA is paying to the bank?
Solution
First, convert the percentages to decimals:
Now apply the formula:
Subtract to isolate the real rate:
Convert back to a percentage:
So, the real interest rate is .
If the question instead requires recalculating the money rate of interest, multiply the real interest factor by inflation:
Subtract and convert to a percentage:
Functions of a central bank/reserve bank of a country
Supervision of the money supply and the banking system of a country
A central bank manages the country’s money supply and supports the stability of the banking system.
One way it influences the economy is by changing interest rates, especially the base rate (the rate at which commercial banks borrow from the central bank). The basic chain works like this:
- If the base rate increases, commercial banks face higher borrowing costs.
- Commercial banks typically pass this on by increasing the interest rates they charge customers.
- If the base rate decreases, commercial banks can usually reduce the rates they charge customers.
You’ll often see base rate changes reported in basis points:
- 100 base points = 1%
So, if a central bank increases the base rate by 100 base points, it has increased the rate by 1%. You can interpret other changes using the same conversion.
This process is known as quantitative easing.
Banker to the banks
The central bank supplies money to commercial banks. This supports everyday banking activity, including:
- cash withdrawals from ATMs
- electronic transfers and payments
Banker to the government
The central bank also acts as the government’s bank. For example:
- The government may borrow directly from the central bank for large projects.
- When the government issues bonds, it issues them through the central bank.
Lender of last resort
As a lender of last resort, the central bank provides emergency funding when other borrowing options aren’t available. This can apply to:
- commercial banks that need urgent liquidity
- the government, especially when it needs large amounts of funding and repayment may take longer