Used in both industry and occupation contexts, Shift Share is a standard method of regional economic analysis that helps identify whether job change in an industry/occupation in a region is due to national factors–the “rising tide lifts all boats” phenomenon–or whether it’s due to factors within the region of study itself.
An industry/occupation could be growing/declining in a region because of one or several of the following factors:
Growth Effect, the overall growth/decline of the entire national economy;
Industry/Occupation Mix Effect, the growth/decline of the industry/occupation in question at a national level;
Competitive Effect, growth/decline that cannot be explained completely by national trends and therefore highlights something unique about the region of study.
The most important of the three is Competitive Effect, which identifies region-specific factors as being responsible for the growth/decline of the industry/occupation in question.
Expected Change shows the expected growth/decline for the industry/occupation in region in question given the National Growth Effect and the Industry/Occupation Mix Effect. The Competitive Effect is the leftover effect (if any) that cannot be explained by the National Growth Effect and Industry/Occupation Mix Effects as shown in the Expected Change metric.
For a deeper dive into Shift Share, see this article.
Source: Lightcast’s proprietary employment data.