Expansionary policy is a type of policy used to boost economic growth and prosperity, often during a recession. Expansionary policy seeks to stimulate the economy by expanding the money supply, reducing taxes and other costs, or increasing government spending.

The goal of expansionary policy is to increase aggregate demand in the economy, the total demand for goods and services by consumers, business, and government. In turn, increased demand leads to higher overall prices, wage increases and growth in GDP. Expansionary policies may also help to achieve higher employment levels, thanks to increased demand for labour.

There are two types of expansionary policy: monetary and fiscal. Fiscal policy involves directly influencing the supply of money and tax rates, often by means of government spending. Examples of fiscal stimulus measures might include government aid packages, bailouts, and other public investments.

Monetary policy, on the other hand, utilizes conventional monetary tools such as interest rate cuts, bond purchases, and openly printing money. Expansionary monetary policy aims to increase the money supply, causing a drop in interest rates and stimulating investment and consumer spending.

Although expansionary policy is an effective way of stimulating the economy, it can come with a hefty cost. Expansionary policies often cause inflation, reducing the value of money, as a result of an increase in the money supply. This might be a side effect economists accept when trying to pull an economy out of a recession. In addition, overly-expansionary policies can lead to inefficient resource allocation and excessive government debt, among other problems.

Despite their potential costs and risks, expansionary policy remains popular, particularly in times of economic difficulty. By providing stimuli, the government hopes to reduce the severity of economic downturns and limit the damaging impact of financial crises. As the world has become increasingly interconnected, the scale and timing of expansionary policy has become more important, with countries around the world coordinating stimulus measures in order to optimize their economic benefit.

In summary, expansionary policy is a powerful tool for stimulating the economy, but it can have risks and costs. Whether the risk is worth taking depends on the individual circumstances of each country's economy.