Context is at: http://tinyurl.com/qc7uhbn National and regional economies are unmanageably complicated. Statistics offices need simplified models. Though simplified, the models need to capture the important features. One way to do it is to divide economic activities into major "sectors." One such classification is: agriculture, manufacturing, services, and knowledge-based activity. Statistics offices around the world agree that this is a good way to do it. This classification into these four sectors is widely accepted.

As far as I understand; statistics offices are studying on the economic activities of major sectors to understand the economic structure of national and regional economies. Split means the distibution of total economic activies between major sectors and capture means to understand .