Passage Summary: A company used to own half the market and now owns a quarter. Since they make the same profit per unit, the author assumes their total profit has been cut in half.

Conclusion: Wilson's total net income from hair dryer sales is currently half of what it was five years ago.

Reasoning: The company's market share dropped from 50 percent to 25 percent over five years, while the profit earned per unit sold remained the same.

Analysis: This argument suffers from a classic confusion between percentages and absolute numbers. Market share is a percentage of the total market, not a fixed number of sales. If the total market for hair dryers doubled or tripled in size over those five years, a 25 percent share today could actually represent the same number of units (or more) as a 50 percent share did previously. The author's flaw is failing to consider that the total size of the market might have changed, which would decouple market share from total income.