Sentence:  Economics is a messy discipline: too fluid to be a science, too rigorous to be an art. Perhaps it is fitting that economists' most-used metric, gross domestic product (GDP), is a tangle too. GDP measures the total value of output in an economic <WSD>territory</WSD>. Its apparent simplicity explains why it is scrutinised down to tenths of a percentage point every month. 
Meaning of the word marked with <WSD> tags:  A geographic area under control of a single governing entity such as state or municipality; an area whose borders are determined by the scope of political power rather than solely by natural features such as rivers and ridges.