This is related to Fiscal policy and the multiplier effect.
http://www.tutor2u.net/blog/index.php/economics/comments/qa-what-is-the-accelerator-effect/
Notes on the multiplier and accelerator
http://portal.kings-ely.cambs.sch.uk/Senior%20School/Departments/Economics/Pupils/Document%20Library/Year%2012%20Economics/Module%202%20-%20Macro%20Economics/OCR%20Unit%20F582%20tutor2u%20notes/Multiplier%20and%20Accelerator%20Effects.pdf