The exceptions to the law of demand are the special cases in which quantity demanded rises as price rises (or falls as price falls) — so the demand curve slopes upward instead of the usual downward slope.

The recognised exceptions

• Giffen goods — highly inferior staple goods (Sir Robert Giffen's classic case). When their price rises, the poor consumer becomes so much worse off in real terms that they buy more of the cheap staple and less of costlier substitutes. Here the negative income effect outweighs the substitution effect.
• Conspicuous / Veblen goods — luxury goods (diamonds, designer items) bought for prestige. A higher price signals higher status, so demand rises with price (the Veblen effect).
• Conspicuous necessities — goods that have become status symbols of modern life; demand persists or rises despite higher prices.
• Goods of speculation — when buyers expect prices to rise further, a price rise today can increase today's demand (e.g. shares).
• Emergencies / abnormal situations — during war, famine or crisis, people buy more even at higher prices out of fear of scarcity. …