prices in times of shortage – common at the time – was dangerous economically as it acted as a disincentive to production. Generally, Le Pesant advocated less government interference in the grain market, as any such interference would generate "anticipations" which would prevent the policy from working. For instance, if the government bought corn abroad, some people would speculate that there was likely to be a shortage and would buy more corn, leading to higher prices and more of a shortage. This was an early example of advocacy of free trade. In anonymously published tracts, Vauban proposed a system known as La dîme royale: this involved major simplification of the French tax code by switching to a relatively flat tax on property and trade. Vauban's use of statistics contrasted with earlier empirical methods in economics. The event that led Mirabeau to devote himself to political economy was undoubtedly his work on a manuscript of Richard Cantillon's Essai sur la nature du commerce en général, which he had in his possession as early as 1740. He elaborated a commentary of this text that gradually became his Ami des hommes. Around the time of the Seven Years' War between France and England (1756–63), the physiocracy movement grew. Several journals appeared, signaling an increasing audience in France for new economic ideas. Among the most important were the Journal Œconomique (1721–72), which promoted agronomy and rational husbandry and the Journal du commerce (1759–62), which was heavily influenced by the Irishman Richard Cantillon (1680–1734), both dominated by physiocrats; the Journal de l'agriculture, du commerce et des finances (1765–74) and the Ephémérides du citoyen (1767–72 and 1774–76). Also, Vincent de Gournay (1712–1759), the Intendant du commerce, brought together a group of young researchers including François Véron Duverger de Forbonnais (1722–1800) and one of the two most famous physiocrats, Anne-Robert-Jacques Turgot (1727–1781). The other, François Quesnay (1694–1774), was among those writing prolifically in contemporaneous journals. In the 19th century Henry George in the United States advocated the collection of land rent as the primary if not the sole source of public revenue. Tableau économique The Tableau économique or Economic Table is an economic model first described by François Quesnay in 1759, which laid the foundation of the physiocrats’ economic theories. It also contains the origins of modern ideas on the circulation of wealth and the nature of interrelationships in the economy. The model Quesnay created consisted of