Tag: Quantitative Modeling

Interest rates are very powerful and intriguing mathematical concepts. Our banking and finance sector revolves around these interest rates. One minor change in these rates could have tremendous and astonishing impacts over the economy.

Interest is the amount charged by the lender from the borrower on the principal loan sum. It is basically the cost of renting money. And, the rate at which interest is charged on the principal sum is known as the interest rate.

These concepts are categorized into type of interests

• Simple Interest
• Compound Interest

Simple Interest

Simple Interest because as the name suggests it is simple and comparatively easy to comprehend.

Simple interest is that type of interest which once credited does not earn interest on itself. It remains fixed over time.

The formula to calculate Simple Interest is

SI = {(P x R x T)/ 100}   

Where,

P = Principal Sum (the original loan/ deposited amount)

R = rate of interest (at which the loan is charged)

T = time period (the duration for which money is borrowed/ deposited)

So, if P amount is borrowed at the rate of interest R for T years then the amount to be repaid to the lender will be

A = P + SI

Compound Interest:

This the most usual type of interest that is used in the banking system and economics. In this kind of interest along with one principal further earns interest on it after the completion of 1-time period. Suppose an amount P is deposited in an account or lent to the borrower that pays compound interest at the rate of R% p.a. Then after n years the deposit or loan will accumulate to:

P ( 1 + R/100)ⁿ

Compound Interest when Compounded Half Yearly

Example 2:

Find the compound interest on Rs 8000 for 3/2 years at 10% per annum, interest is payable half-yearly.

Solution: Rate of interest = 10% per annum = 5% per half –year. Time = 3/2 years = 3 half-years

Original principal = Rs 8000.

$$Interestforthefirsthalfyear=\; (\frac{8000\times 5\times \mathrm{1)/}}{100}=420$$

Amount at the end of the first half-year = Rs 8000 +Rs 400 = Rs 8400

Principal for the second half-year = Rs 8400

$$Interestforthesecondhalfyear=\; (\frac{8400\times 5\times \mathrm{1)/}}{100}=420$$

Amount at the end of the second half year = Rs 8400 +Rs 420 = Rs 8820

$$Interestforthethirdhalfyear=\; (\frac{8820\times 5\times \mathrm{1)/}}{100}=Rs441$$

Amount at the end of third half year = Rs 8820 + Rs 441= Rs 9261.

Therefore, compound interest= Rs 9261- Rs 8000 = Rs 1261.

Therefore,

$$\mathrm{Co}mpoundinterest=Rs9261-Rs8000=Rs1261$$

The Effective Annual Rate (EAR) is the interest rate that is adjusted for compounding over a given period. Simply put, the effective annual interest rate is the rate of interest that an investor can earn (or pay) in a year after taking into consideration compounding.

The Effective Annual Interest Rate is also known as the effective interest rate, effective rate, or the annual equivalent rate. Compare it to the Annual Percentage Rate (APR) which is based on simple interest.

The EAR formula for Effective Annual Interest Rate:

Where:

i = stated annual interest rate

n = number of compounding periods

Importance of Effective Annual Rate

The Effective Annual Interest Rate is an important tool that allows the evaluation of the true return on an investment or true interest rate on a loan.

The stated annual interest rate and the effective interest rate can be significantly different, due to compounding. The effective interest rate is important in figuring out the best loan or determining which investment offers the highest rate of return.

In the case of compounding, the EAR is always higher than the stated annual interest rate.

Whether effective and nominal rates can ever be the same depends on whether interest calculations involve simple or compound interest. While in a simple interest calculation effective and nominal rates can be the same, effective and nominal rates will never be the same in a compound interest calculation. Although short-term notes generally use simple interest, the majority of interest is calculated using compound interest. To a small-business owner, this means that except when taking out a short-term note, such as loan to fund working capital, effective and nominal rates can be the same for most every other credit purchase or cash investment.

Nominal Vs. Effective Rate

Nominal rates are quoted, published or stated rates for loans, credit cards, savings accounts or other short-term investments. Effective rates are what borrowers or investors actually pay or receive, depending on whether or how frequently interest is compounded. When interest is calculated and added only once, such as in a simple interest calculation, the nominal rate and effective interest rates are equal. With compounding, a calculation in which interest is charged on the loan or investment principal plus any accrued interest up to the point at which interest is being calculated, however, the difference between nominal and effective increases exponentially according to the number of compounding periods. Compounding can take place daily, monthly, quarterly or semi-annually, depending on the account and financial institution regulations.

Simple Interest

The formula for calculating simple interest is “P x I x T” or principle multiplied by the interest rate per period multiplied by the time the money is being borrowed or invested. This formula illustrates that because interest is always being calculated on the principal amount, regardless of the time period involved, the nominal and effective rates will always be equal . If a small-business owner takes out a $5,000 simple interest loan at a nominal rate of 10 percent, $500 of interest will be added to the loan will each year, regardless of the number of years. To illustrate, just as $5,000 x 0.10 x 1 equals $500, $5,000 x 0.10 x 5 equals $2,500 or $500 per year. The nominal and effective rates of 10 percent in both calculations are equal.

Compound Interest

The formula for calculating compound interest shows how nominal and effective rates will never be equal. The formula is “P x (1 + i)n – P” where “n” is the number of compounding periods. In a compound interest calculation, the only time interest is charged or added to the principal is in the first compounding period. The base for each subsequent compounding period is the principal plus any accrued interest. If a small-business owner takes out a one-year $5,000 compound-interest loan at a nominal interest rate of 10 percent, where interest is compounded monthly, total interest that accumulates over the year is $5,000 x (1 + .10)5 – $5,000 or $550. The nominal rate of 10 percent and the effective rate of 11 percent clearly aren’t the same.

Effect On Small Business Owners

It’s crucial that whether the intent is to borrow or invest, small-business owners pay close attention to effective and nominal rates as well as the number of compounding periods. Compounding interest not only creates distance between nominal and effective rates but also works in favor of lenders. For example, a bank, credit card company or auto dealership might advertise a low nominal rate, but compound interest monthly. This in effect significantly increases the total amount owed. This is one reason why lenders advertise or quote nominal rather than effective rates in lending situations.

The rate charged by the Reserve Bank from the commercial banks and the depository institutions for the overnight loans given to them. The discount rate is fixed by the Federal Reserve Bank and not by the rate of interest in the market.

Also, the discount rate is considered as a rate of interest which is used in the calculation of the present value of the future cash inflows or outflows. The concept of time value of money uses the discount rate to determine the value of certain future cash flows today. Therefore, it is considered important from the investor’s point of view to have a discount rate for the comparison of the value of cash inflows in the future from the cash outflows done to take the given investment.

Interest Rate

If a person called as the lender lends money or some other asset to another person called as the borrower, then the former charges some percentage as interest on the amount given to the later. That percentage is called the interest rate. In financial terms, the rate charged on the principal amount by the bank, financial institutions or other lenders for lending their money to the borrowers is known as the interest rate. It is basically the borrowing cost of using others fund or conversely the amount earned from the lending of funds.

There are two types of interest rate:

• Simple Interest: In Simple Interest, the interest for every year is charged on the original loan amount only.
• Compound Interest: In Compound Interest, the interest rate remains same but the sum on which the interest is charged keeps on changing as the interest amount each year is added to the principal amount or the previous year amount for the calculation of interest for the coming year.