 In many instances, large movements in food and energy prices arise because of supply disruptions such as drought or OPEC-led cutbacks in production.This was introduced in the early 1970s when food and especially oil prices were quite volatile, and the Fed wanted an index that was less subject to short term shocks.However, on January 25, 2012, the Fed announced they would stop using the core CPI and rely instead on the personal consumption expenditures price index.