What assumptions about the economy must be true for the invisible hand to work? To what extent are those assumptions valid in the real world?

The invisible hand is a metaphor to describe the mechanism through which individual decisions driven by self-interest can lead to an aggregate outcome that benefits society. In this context, when individuals and firms make decisions in their own interest, resource allocation becomes efficient, promoting overall welfare. The concept is associated with the idea of laissez-faire economics, where a minimal government intervention is advocated.

There are multiple assumptions necessary for the invisible hand to work efficiently. Some of them are: a. Perfect competition: The market structure must be perfectly competitive, implying that there are numerous buyers and sellers, products are homogenous, and there is perfect information for everyone. b. Rationality: Economic agents (individuals, households, and firms) must be rational and act in their best self-interest to maximize utility or profits. c. No externalities: There should be no external costs or benefits associated with the production or consumption of goods. In other words, the market prices should reflect the true cost and benefit of the product. d. Perfect mobility of factors of production: Labor and capital must be free to move within the economy without any restrictions, ensuring efficient allocation of resources. e. Stable equilibrium: The economy must be stable, with supply and demand being in balance, and when disturbed, the invisible hand should bring it back to the equilibrium.

In reality, these assumptions don't always hold true. Here's the extent to which they are valid in the real world: a. Perfect competition: Many markets exhibit some degree of imperfect competition, such as oligopolies or monopolies, leading to market inefficiencies and imbalances. b. Rationality: Behavioral economics has shown that human decision-making isn't always rational due to cognitive biases, myopia, and other factors. c. No externalities: Real-world markets often have positive or negative externalities (i.e., pollution, congestion, public goods) that can adversely affect societal welfare and requires government intervention to correct the market failure. d. Perfect mobility of factors of production: There are various limitations to labor and capital mobility (e.g., legal and regulatory barriers, cultural differences, limited access to finance) that impede the efficient allocation of resources in an economy. e. Stable equilibrium: Fluctuations in aggregate demand and supply can lead to economic cycles, recessions, and depressions calling for government intervention to stabilize the economy. In conclusion, while the assumptions required for the invisible hand to work provide a useful theoretical framework for understanding how markets can be self-regulating, they often don't hold true in the real world. Hence, some level of government intervention may be necessary to address market failures and ensure the efficient allocation of resources and overall societal welfare.