2.3 Profitability Ratios & DuPont

Margin Ratios

Margin ratios express profit at different income-statement levels as a percentage of sales, isolating where profit is earned or lost.

• Gross profit margin = gross profit / net sales = (sales - COGS) / sales. Reflects pricing power and production cost control.
• Operating profit margin = operating income (EBIT) / net sales. Reflects core operations before financing and taxes.
• Net profit margin = net income / net sales. The bottom line after interest, taxes, and all items.

Reading the three together reveals where profit erodes. If gross margin is stable but operating margin falls, overhead or selling costs rose. If operating margin holds but net margin drops, interest or taxes increased.

Quick Margin Example

Assume sales $1,000, COGS $600, operating expenses $250, interest $30, taxes $36. Then EBIT = 1,000 - 600 - 250 = $150 and net income = 150 - 30 - 36 = $84.

Return Ratios

Return ratios compare profit to the capital that produced it.

• Return on assets (ROA) = net income / average total assets. Profit per dollar of assets, ignoring how those assets are financed.
• Return on equity (ROE) = net income / average shareholders' equity. Profit per dollar owners invested.
• Return on invested capital (ROIC) = NOPAT / invested capital, where NOPAT = EBIT x (1 - tax rate) and invested capital = interest-bearing debt + equity. ROIC measures the return earned for all capital providers and is compared against the weighted-average cost of capital (WACC).

Key contrast: ROA ignores financing; ROE rises when a firm adds profitable debt because leverage magnifies returns to owners. A firm can lift ROE simply by borrowing, even without improving operations, so leverage must be examined alongside it.

ROIC vs WACC: The Value Test

Return on invested capital answers the central question of value creation: is the firm earning more on its capital than that capital costs?

• If ROIC > WACC, the firm creates value for investors with each dollar deployed.
• If ROIC < WACC, the firm destroys value even if it reports positive net income.

Example: NOPAT = EBIT $150 x (1 - 0.25 tax) = $112.50; invested capital = debt $600 + equity $400 = $1,000. ROIC = 112.50 / 1,000 = 11.25%. If WACC is 9%, the firm earns a 2.25-point spread and is creating value. This connects financial-statement analysis to the corporate-finance domain that follows.

The DuPont Model (3-Step)

The DuPont identity decomposes ROE into three drivers, exposing what actually moves returns:

ROE = Net Profit Margin x Total Asset Turnover x Equity Multiplier

• Net profit margin = net income / sales (profitability)
• Total asset turnover = sales / total assets (efficiency)
• Equity multiplier = total assets / equity (financial leverage)

Multiplying these, sales and assets cancel, leaving net income / equity = ROE. The power is diagnostic: two firms with identical ROE can have completely different profiles. One earns it through high margins (a luxury brand), another through high turnover (a discount retailer), and a third through heavy leverage (a bank).

Worked Decomposition (3-Step)

Assume: net income $80, sales $1,000, total assets $800, equity $400.

Check: net income / equity = 80 / 400 = 20.0%. If ROE later rises from 20% to 24% while margin and turnover are flat, the equity multiplier must have increased, meaning the firm simply took on more debt, not that operations improved.

This diagnostic discipline is why examiners favor DuPont questions. They may hold two of the three drivers constant and ask which one moved ROE, or hand you the three components and ask you to multiply. Memorize the order: profitability, then efficiency, then leverage.

The Extended 5-Step DuPont

The 5-step (extended) DuPont splits net margin further to separate operating performance from financing and tax effects:

ROE = Tax Burden x Interest Burden x Operating Margin x Asset Turnover x Equity Multiplier

• Tax burden = net income / pre-tax income (EBT)
• Interest burden = EBT / EBIT
• Operating margin = EBIT / sales
• Asset turnover = sales / total assets
• Equity multiplier = total assets / equity

The first three components multiply back to net margin (NI/EBT x EBT/EBIT x EBIT/sales = NI/sales). This lets an analyst see whether a rising ROE came from better operations (operating margin), cheaper financing or less interest (interest burden), or favorable taxes (tax burden), versus pure leverage.

A lower tax burden ratio actually means higher taxes (net income is a smaller fraction of pre-tax income), and a lower interest burden ratio means more interest expense. Read these two as fractions retained after tax and after interest, respectively; closer to 1.0 is better for owners.