Countries have different levels of development internally and compared to each other. Development can be measured in various ways - including economic and human development.
Countries within the EU have different levels of development. In general, the older members of the EU have higher levels of GNPGNP: Gross National Product - Total value of all the good and services produced in a country in a year along with income from abroad. It is one way of measuring the wealth of a country. than those that have joined the EU recently. These countries form the economic coreeconomic core: An area which has more employment and economic opportunities than the surrounding area. It may not be at the geographical centre of the area. of Europe. The UK and France are two examples. Countries forming the economic peripheryeconomic periphery: Areas which have less employment opportunities and a weaker economy. This may not be on the physical edge of a region, just an economic edge. of the EU tend to be newer members of the EU, such as Bulgaria.
Measuring development in other ways (such as using the Human Development IndexHuman Development Index: A statistical index used to rank the 'human development' of countries, on a scale between 0 and 1. Covers life expectancy, education and living standards.) also shows these differences between countries in the EU, but not as clearly.
The map below shows the countries which were members of the EU in 2011.

Countries in the EU.
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