Changes in price indices - Double bar chart

"A price index (plural: “price indices” or “price indexes”) is a normalized average (typically a weighted average) of price relatives for a given class of goods or services in a given region, during a given interval of time. It is a statistic designed to help to compare how these price relatives, taken as a whole, differ between time periods or geographical locations.
Price indexes have several potential uses. For particularly broad indices, the index can be said to measure the economy's general price level or a cost of living. More narrow price indices can help producers with business plans and pricing. Sometimes, they can be useful in helping to guide investment." [Price index. Wikipedia]
The double bar chart example "Changes in price indices" was redrawn from the website of the United States Department of Agriculture Economic Research Service. [ers.usda.gov/ data-products/ chart-gallery/ detail.aspx?chartId=29456&ref=collection#.Ue5MMaxad5I]
The double bar chart example "Changes in price indices" was created using the ConceptDraw PRO diagramming and vector drawing software extended with the Bar Graphs solution from the Graphs and Charts area of ConceptDraw Solution Park.