What Is Average Cost Method?

Average cost method assigns a cost to inventory items based on the total cost of goods purchased or produced in a period divided by the total number of items purchased or produced. Average cost method is also known as weighted-average method.

Understanding the Average Cost Method

Businesses that sell products to customers have to deal with inventory, which is either bought from a separate manufacturer or produced by the company itself. Items previously in inventory that are sold off are recorded on a company’s income statement as cost of goods sold (COGS). COGS is an important figure for businesses, investors, and analysts as it is subtracted from sales revenue to determine gross margin on the income statement. To calculate the total cost of goods sold to consumers during a period, different companies use one of three inventory cost methods:

Average cost method uses a simple average of all similar items in inventory, regardless of purchase date, followed by a count of final inventory items at the end of an accounting period. Multiplying the average cost per item by the final inventory count gives the company a figure for the cost of goods available for sale at that point. The same average cost is also applied to the number of items sold in the previous accounting period to determine the COGS.

Example of Average Cost Method

For example, consider the following inventory ledger for Sam’s Electronics:

What is the Average Daily Balance Method?

The average daily balance is a common accounting method that calculates interest charges by considering the balance invested or owed at the end of each day of the billing period, rather than the balance invested or owed at the end of the week, month, or year.

Understanding the Average Daily Balance Method

The federal Truth-In-Lending-Act (TILA) requires lenders to disclose their method of calculating finance charges, as well as annual percentage rates (APR), fees, and other terms, in their terms and conditions statement. Providing these details makes it easier to compare different credit cards.

TILA permits the interest owed on credit card balances to be calculated in various different ways. The most common methods are:

• Average daily balance method: Uses the balance on each day of the billing cycle, rather than an average balance throughout the billing cycle, to calculate finance charges.
• Previous balance method: Interest charges are based on the amount owed at the beginning of the previous month’s billing cycle.
• Adjusted balance method: Bases finance charges on the amount(s) owed at the end of the current billing cycle after credits and payments have been posted.

How the Average Daily Balance Method Works

The average daily balance totals each day’s balance for the billing cycle and divides by the total number of days in the billing cycle. Then, the balance is multiplied by the monthly interest rate to assess the customer’s finance charge—dividing the cardholder’s APR by 12 calculates the monthly interest rate. However, if the lender or card issuer uses a method that compounds interest daily, the interest associated with the day’s ending balance gets added to the next day’s beginning balance. This will result in higher interest charges and the reader should confirm which method is being used.

The average daily balance credits a customer’s account from the day the credit card company receives a payment. To assess the balance due, the credit card issuer sums the beginning balance for each day in the billing period and subtracts any payments as they arrive and any credits made to the customer’s account that day.

Cash advances are usually included in the average daily balance. The total balance due may fluctuate daily because of payments and purchases.

Average Daily Balance Method Example

A credit card has a monthly interest rate of 1.5 percent, and the previous balance is $500. On the 15th day of a billing cycle, the credit card company receives and credits a customer’s payment of $300. On the 18th day, the customer makes a $100 purchase.

The average daily balance is ((14 x 500) + (3 x 200) + (13 x 300)) / 30 = (7,000 + 600 + 3,900) / 30 = 383.33. The bigger the payment a customer pays and the earlier in the billing cycle the customer makes a payment, the lower the finance charges assessed. The denominator, 30 in this example, will vary based on the number of days in the billing cycle for a given month.

Average Daily Balance Method Vs. Adjusted Balance Method Vs. Previous Balance Method

Interest charges using the average daily balance method should be lower than the previous balance method, which charges interest based on the amount of debt carried over from the previous billing cycle to the new billing cycle. On the other hand, the average daily balance method will likely incur higher interest charges than the adjusted balance method because the latter bases finance charges on the current billing period’s ending balance.

Card issuers use the adjusted balance method much less frequently than either the average daily balance method or the previous balance method.

Special Considerations

Some credit card companies previously used the double-cycle billing method, assessing a customer’s average daily balance over the last two billing cycles.

Double-cycle billing can add a significant amount of interest charges to customers whose average balance varies greatly from month to month. The Credit CARD Act of 2009 banned double-cycle billing on credit cards.

What Is Average Life?

The average life is the length of time the principal of a debt issue is expected to be outstanding. Average life does not take into account interest payments, but only principal payments made on the loan or security. In loans, mortgages, and bonds, the average life is the average period of time before the debt is repaid through amortization or sinking fund payments.

Investors and analysts use the average life calculation to measure the risk associated with amortizing bonds, loans, and mortgage-backed securities. The calculation gives investors an idea of how quickly they can expect returns and provides a useful metric for comparing investment options. In general, most investors will choose to receive their financial returns earlier and will, therefore, choose the investment with the shorter average life.

Understanding Average Life

Also called the weighted average maturity and weighted average life, the average life is calculated to determine how long it will take to pay the outstanding principal of a debt issue, such as a Treasury Bill (T-Bill) or bond. While some bonds repay the principal in a lump sum at maturity, others repay the principal in installments over the term of the bond. In cases where the bond’s principal is amortized, the average life allows investors to determine how quickly the principal will be repaid.

The payments received are based on the repayment schedule of the loans backing the particular security, such as with mortgage-backed securities (MBS) and asset-backed securities (ABS). As borrowers make payments on the associated debt obligations, investors are issued payments reflecting a portion of these cumulative interest and principal payments.

Calculating the Average Life on a Bond

To calculate the average life, multiply the date of each payment (expressed as a fraction of years or months) by the percentage of total principal that has been paid by that date, add the results, and divide by the total issue size.

For example, assume an annual-paying four-year bond has a face value of $200 and principal payments of $80 during the first year, $60 for the second year, $40 during the third year, and $20 for the fourth (and final) year. The average life for this bond would be calculated with the following formula:

($80 x 1) + ($60 x 2) + ($40 x 3) + ($20 x 4) = 400

Then divide the weighted total by the bond face value to get the average life. In this example, the average life equals 2 years (400 divided by 200 = 2).

This bond would have an average life of two years against its maturity of four years.

Mortgage-Backed and Asset-Backed Securities

In the case of an MBS or ABS, the average life represents the average length of time required for the associated borrowers to repay the loan debt. An investment in an MBS or ABS involves purchasing a small portion of the associated debt that is packaged within the security.

The risk associated with an MBS or ABS centers on whether the borrower associated with the loan will default. If the borrower fails to make a payment, the investors associated with the security will experience losses. In the financial crisis of 2008, a large number of defaults on home loans, particularly in the subprime market, led to significant losses in the MBS arena.

Special Considerations

While certainly not as dire as default risk, another risk bond investors face is prepayment risk. This occurs when the bond issuer (or the borrower in the case of mortgage-backed securities) pays back the principal earlier than scheduled. These prepayments will reduce the average life of the investment. Because the principal is paid back early, the investor will not receive future interest payments on that part of the principal.

This interest reduction can represent an unexpected challenge for investors of fixed-income securities dependent on a reliable stream of income. For this reason, some bonds with payment risk include prepayment penalties.

What Is Average Annual Growth Rate (AAGR)?

The average annual growth rate (AAGR) reports the mean increase in the value of an individual investment, portfolio, asset, or cash flow on an annualized basis. It doesn’t take compounding into account.

Formula for Average Annual Growth Rate (AAGR)

$\begin{aligned} &AAGR = \frac{GR_A + GR_B + \dotso + GR_n}{N} \\ &\textbf{where:}\\ &GR_A=\text{Growth rate in period A}\\ &GR_B=\text{Growth rate in period B}\\ &GR_n=\text{Growth rate in period }n\\ &N=\text{Number of payments}\\ \end{aligned}$​AAGR=NGRA​+GRB​+…+GRn​​where:GRA​=Growth rate in period AGRB​=Growth rate in period BGRn​=Growth rate in period nN=Number of payments​

Understanding the Average Annual Growth Rate (AAGR)

The average annual growth rate helps determine long-term trends. It applies to almost any kind of financial measure including growth rates of profits, revenue, cash flow, expenses, etc. to provide the investors with an idea about the direction wherein the company is headed. The ratio tells you your average annual return.

The average annual growth rate is a calculation of the arithmetic mean of a series of growth rates. AAGR can be calculated for any investment, but it will not include any measure of the investment’s overall risk, as measured by its price volatility. Furthermore, the AAGR does not account for periodic compounding.

AAGR is a standard for measuring average returns of investments over several time periods on an annualized basis. You’ll find this figure on brokerage statements and in a mutual fund’s prospectus. It is essentially the simple average of a series of periodic return growth rates.

One thing to keep in mind is that the periods used should all be of equal length—for instance, years, months, or weeks—and not to mix periods of different duration.

AAGR Example

The AAGR measures the average rate of return or growth over a series of equally spaced time periods. As an example, assume an investment has the following values over the course of four years:

• Beginning value = $100,000
• End of year 1 value = $120,000
• End of year 2 value = $135,000
• End of year 3 value = $160,000
• End of year 4 value = $200,000

The formula to determine the percentage growth for each year is:

$\text{Simple percentage growth or return} = \frac{\text{ending value}}{\text{beginning value}} – 1$Simple percentage growth or return=beginning valueending value​−1

Thus, the growth rates for each of the years are as follows:

• Year 1 growth = $120,000 / $100,000 – 1 = 20%
• Year 2 growth = $135,000 / $120,000 – 1 = 12.5%
• Year 3 growth = $160,000 / $135,000 – 1 = 18.5%
• Year 4 growth = $200,000 / $160,000 – 1 = 25%

The AAGR is calculated as the sum of each year’s growth rate divided by the number of years:

$AAGR = \frac{20 \% + 12.5 \% + 18.5 \% + 25 \%}{4} = 19\%$AAGR=420%+12.5%+18.5%+25%​=19%

In financial and accounting settings, the beginning and ending prices are usually used. Some analysts may prefer to use average prices when calculating the AAGR depending on what is being analyzed.

As another example, consider the five-year real gross domestic product (GDP) growth for the United States over the last five years. The U.S. real GDP growth rates for 2017 through 2021 were 2.3%, 2.9%, 2.3%, -3.4%, and 5.7%, respectively. Thus, the AAGR of U.S. real GDP over the last five years has been 1.96%, or (2.3% + 2.9% + 2.3% + -3.4% + 5.7%) / 5.

AAGR vs. Compound Annual Growth Rate

AAGR is a linear measure that does not account for the effects of compounding. The above example shows that the investment grew an average of 19% per year. The average annual growth rate is useful for showing trends; however, it can be misleading to analysts because it does not accurately depict changing financials. In some instances, it can overestimate the growth of an investment.

For example, consider an end-of-year value for year 5 of $100,000 for the AAGR example above. The percentage growth rate for year 5 is -50%. The resulting AAGR would be 5.2%; however, it is evident from the beginning value of year 1 and the ending value of year 5, the performance yields a 0% return. Depending on the situation, it may be more useful to calculate the compound annual growth rate (CAGR).

The CAGR smooths out an investment’s returns or diminishes the effect of the volatility of periodic returns. 

Formula for CAGR

$CAGR = \frac{\text{Ending Balance}}{\text{Beginning Balance}}^{\frac{1}{\text{\# Years}}} – 1$CAGR=Beginning BalanceEnding Balance​# Years1​−1

Using the above example for years 1 through 4, the CAGR equals:

$CAGR = \frac{\$200,000}{\$100,000}^{\frac{1}{4}}- 1 = 18.92\%$CAGR=$100,000$200,000​41​−1=18.92%

For the first four years, the AAGR and CAGR are close to one another. However, if year 5 were to be factored into the CAGR equation (-50%), the result would end up being 0%, which sharply contrasts the result from the AAGR of 5.2%.

Limitations of the AAGR

Because AAGR is a simple average of periodic annual returns, the measure does not include any measure of the overall risk involved in the investment, as calculated by the volatility of its price. For instance, if a portfolio grows by a net of 15% one year and 25% in the next year, the average annual growth rate would be calculated to be 20%.

To this end, the fluctuations occurring in the investment’s return rate between the beginning of the first year and the end of the year are not counted in the calculations thus leading to some errors in the measurement.

A second issue is that as a simple average it does not care about the timing of returns. For instance, in our example above, a stark 50% decline in year 5 only has a modest impact on total average annual growth. However, timing is important, and so CAGR may be more useful in understanding how time-chained rates of growth matter.