 Countries come in all shapes and sizes. They are made up of many different types of people from many different backgrounds. How do we ensure that all these diverse people get sufficient political representation? One solution is a political system called federalism. Only 30 of the world's 195 countries are federations. Yet together these 30 countries represent 40% of the world's population. In other words, almost half the world's people are governed under a federal political system. But what exactly is federalism and why might a country consider adopting a federal system? The answer is that federalism provides a practical way for groups of people who have some things in common but also some important differences to live together. They do this by sharing powers over the things they have in common, like international trade for example. At the same time these groups maintain some level of self-rule over those things that concern their own interests. For example, education, primary healthcare and broadcasting. For this reason federalism is often a choice for large countries like India, the United States, Brazil, Germany, Mexico and Nigeria. It is also often chosen by countries which have a very diverse population living in different parts of the country who wish to preserve their own identities. Belgium, Switzerland and Nepal are such countries. As a response to these challenges of size and diversity, federalism can take various forms. And since no single country is exactly like another, no federal system is exactly alike either. Nevertheless federalism does have some distinct defining characteristics which make it different from other forms of decentralization. The first characteristic is that the federal systems have at least two levels of government. There is a central level of government, also sometimes known as the federal or union level which governs the entire country in relation to issues of importance to everyone. This usually means matters like defence, the armed forces, foreign policy, trade, citizenship, macroeconomic policy and national infrastructure like ports and airports. The second level of government operates in the states, regions, provinces or other entities into which the country is divided. Each of these has control over certain types of policy and legislation, usually of immediate relevance to its own people. This often includes delivery of services such as roads and public health services and issues of cultural significance like education and broadcasting. These are of course just typical examples. The level of decentralization and the exact distribution of powers and responsibilities varies greatly between federations depending on their needs and circumstances. For example in Nigeria environmental protection is a state matter but in Malaysia it has run along federal lines. In some federal systems there are powers which do not belong exclusively to either level of government but are shared between them. In India for example both the Indian parliament and the state legislatures can pass laws on criminal justice and social and economic planning. But if there is incompatibility between them the central level of legislation prevails. A second characteristic of federalism is that it provides processes and mechanisms by which the different states, provinces or regions of the Federation can be included in decision making at the central or union level. Normally this takes the form of another House of Parliament or Senate in which these states, provinces or regions are represented. In Australia and Argentina for example each state is represented in the Senate by an equal number of directly elected senators. In India and Malaysia some members of the upper house are chosen indirectly by the members of the state legislatures. Power sharing is also achieved through cooperation between different levels of government. In Canada a council made up of the heads of provincial governments meets to discuss issues of common interest and to coordinate service delivery. For example although healthcare in Canada is primarily a provincial concern the council has enabled provincial ministers to work together to lower pharmaceutical prices across the entire country. The third characteristic is that in federal systems the powers and responsibilities of the different levels of government are enshrined in a constitution. This protects the federal agreement from being easily changed. In many federations the states, regions or provinces have a veto over constitutional changes so that neither level of government can unilaterally strip the other of its powers. In India any amendments to the constitution which affects the distribution of power between the union and the states must be approved by both the central parliament and the parliaments of the majority of the states. To protect the federal arrangement the constitution needs to include an impartial judicial body such as a supreme court or constitutional court which enforces that agreement in a fair and balanced way. At its heart federalism is a constitutional agreement that enables different communities of people who live in different territories all live together in one country. This agreement recognises that the country is better off united while at the same time protecting the autonomy and rights of its diverse people.