1. Introduction. 1.1. The Law of Market Demand. 1.2. Wald's Axiom. 1.3. Validation of Hypotheses on Market Demand. 1.4. On Individual Behavior: Introspection and Plausibility. 1.5. Substitution and Income Effects. 1.6. Increasing Spread of Households' Demand. 1.7. Family Expenditure Data: Increasing Spread of Conditional Demand. 1.8. Increasing Dispersion -- 2. Market Demand. 2.1. The Distribution of Households' Demand. 2.2. A Microeconomic Model: The Distribution of Households' Characteristics. 2.3. Hicks-Leontief Composite Commodity Theorem. 2.4. Family Expenditure Surveys: The Data -- 3. Increasing Dispersion. 3.1. The Hypothesis of Increasing Dispersion of Households' Demand. 3.2. Examples. 3.3. Empirical Evidence of Increasing Dispersion of Households' Demand -- 4. The Law of Demand. 4.1. The Hypothesis of Increasing Spread of Households' Demand. 4.2. Empirical Evidence of Increasing Spread. 4.3. Deductive Validation of Hypothesis 3 -- App. 1. Monotone Functions -- App. 2. Wald's Axiom.

App. 3. The Weak Axiom of Revealed Preference and the Slutsky Decomposition -- App. 4. Monotonicity of Individual Demand Functions -- App. 5. Spread and Dispersion -- App. 6. The Structure of the Matrix B [actual symbol not reproducible].