Introduction
If you are interested in economics, you may well be thinking about continuing to study the subject after your first degree,making this sort of decision needs a lot of thought, there are many things you should consider when applying. Unlike some other subjects (notably the natural sciences), graduate study in economics is normally a two-stage process: typically a one year Master's followed by a three year PhD. The two stages have different purposes.
Master's Degree
This is primarily a ‘taught' course, like an undergraduate degree. Most are one year, but some last for two, which makes a big difference in terms of cost.
The Master's is designed to train you in the tools needed to become an economist. Some Master's students go on to PhDs, while others become professional economists working in government, international organisations or the private sector. As a consequence it is much more mathematical and empirical than an undergraduate degree. Aside from a dissertation, long essays will be rare. Assessment, like at undergraduate level, tends to be final exam and dissertation.
Doctorate (PhD or DPhil)
This is a research degree. It lasts for three years in theory, but in practice this can stretch to four. Most people will need a Master's already to do it, and have the intention of going into academia, although some professional and governmental institutions increasingly hire top economists with Doctorates. Assessment is of a piece of original research - your thesis. It is normally coupled with a verbal examination called a viva. The majority of Universities refer to this research degree as a PhD, Oxford chose not to and refer to it as a DPhil. A few new Universities have also started to run DPhil's.