Market economies are based on market forces like supply and demand. Mixed economies fall in the middle of market and command economies (where economic choices are governed by some central entity usually the government). The former Soviet Union (USSR) is an example of a command economy where economic choices (what to buy, sell and produce) where made by the government. If Australia is becoming more of a market economy and less of a mixed economy, fewer decisions are made by the government. Here's a diagram of two major types of economies:
Command Economy <-------------- Mixed Economy --------> Market Economy (Government makes the decisions) (A little of both) (Individuals decide)
To protect its local industries and jobs. Placing trade barriers restricts cheaper goods and service that may out-compete those of the local market if allowed to freely compete in the local market.
To protect its population when it feels that the foreign products or services do not meet its national standards and that the goods/services may be harmful for its local population as a measure of national security.
Trade barrier and tariffs are also used as a form of diplomacy. Trade barriers are imposed on good and services from a country that a nation considers hostile.
