Rafael Nadal’s Performance Measured by Elo Ratings

Wrong! - An upward trend requires Elo points to rise over time, while a zero trend would imply no change in Elo points. Neither pattern is observed. The Elo points never increase in any year.

Wrong! - A less steep slope would require smaller decreases in the next year, while a constant slope would imply equal decrease each year. Neither pattern is observed. The decrease never becomes smaller in later years.

Wrong! - Indifference curves become less steep, not steeper. A linear demand curve is a straight line, unlike this curve. A perfectly elastic demand curve is horizontal, which this curve is not.

Wrong! - An opportunity cost would exist only if Nadal’s performance were increasing at the cost of health, but performance is declining. Diminishing marginal utility applies to consumer satisfaction, not to production or athletic performance. The law of demand relates price to quantity demanded, which neither curve shows.