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 an economic theory proposed by Adam Smith, which suggests that individuals pursuing their own self-interests lead to a more efficient allocation of resources in the economy, ultimately benefiting society as a whole. It implies that markets, left to their own devices, will achieve a balance between supply and demand without the need for any intervention by governments or other institutions.

There are several key assumptions that underpin the theoretical foundation of the invisible hand, including: 1. Perfect competition: Numerous buyers and sellers exist in the market, ensuring no single participant can influence the price or the quantity of goods and services. 2. Perfect information: All participants in the market have accurate and complete information about the price, quality, and availability of goods and services. 3. Rational decision-making: Economic agents are rational and act to maximize their well-being (utility for consumers and profit for producers). 4. No externalities: All costs and benefits of production and consumption are internalized by participants, meaning there are no spillover effects on third parties not directly involved in the transaction. 5. No barriers to entry or exit: New firms can enter and existing firms can exit the market freely, allowing for a dynamic and competitive landscape. 6. Mobility of resources: Resources such as labor and capital can move freely between industries and regions, facilitating efficient allocation.

In the real-world, these assumptions often do not hold true: 1. Imperfect competition: Monopolies, oligopolies, and other market structures can allow a few firms or individuals to have significant influence over prices and quantities. 2. Imperfect information: Asymmetric information and misinformation are widespread, leading to market inefficiencies such as adverse selection and moral hazard. 3. Bounded rationality: Decision-making is often influenced by cognitive biases, emotions, and other non-economic factors that deviate from pure rationality. 4. Externalities: Pollution, congestion, and public goods are examples of real-world externalities where the costs and benefits are not fully internalized by market participants. 5. Barriers to entry or exit: Regulations, capital requirements, and network effects can create substantial barriers for new entrants and make it difficult for firms to exit the market. 6. Limited mobility of resources: There are often restrictions on labor mobility, such as immigration laws, skill barriers, and geographical limitations, while capital might be constrained by regulations and other factors.

The deviations from the ideal assumptions of the invisible hand can lead to market failures and inefficiencies, which may require intervention from governments or other institutions. Examples of such interventions include antitrust regulations, environmental policies, and public provisions of education and healthcare. In conclusion, while the invisible hand theory provides an insightful framework for understanding the idealized functioning of an economy, real-world deviations from this framework's assumptions reveal the need for a balanced approach between laissez-faire policies and well-targeted interventions to address market failures and promote economic efficiency.