So I took the country average of the milk, meat, cereals, and oilcrops from the source below. It was only available yearly and up to 2010...(It is slightly different from how the world price index was calculated):
The FAO indices of agricultural producer prices measure the average annual change over time in theselling prices received by farmers (prices at the farm-gate or at the first point of sale. The indices are constructed usingprice data in Standardised Local Currency (SLC).
There are two categories of producer price indices available in FAOSTAT:
Agriculture Producer Price Index This is an aggregate index for all primary crops and livestock products. For a country, theaggregate would include all primary crops and livestock products that are produced in that country, and for which bothproduction and producer price data are available.
Single item indices Price indices are also available for individualcommodities, subject to data availability. Examples of these include:
Wheat Producer Price Index
Rice, paddy Producer Price Index
Maize Producer Price Index
Data source: The main source of data for producer prices and production is the data reported bycountries to FAO. This data is available in FAOSTAT in the Prices and Production data domains. Coverage of countries: Theindices are available for all countries for which both price and production data are disseminated in FAOSTAT. Reference year:The base years of the indices are 2004-2006. The weight used for the aggregate index (Agriculture Producer Price Index) is theaverage production value for the years 2004, 2005 and 2006. Time period: The indices are available from 1999 to the latest yearof data availability. Methodology: The Agriculture Producer Price Index is calculated by the Laspeyres formula. The index iscalculated by summing the SLC price for a given year multiplied by production quantity in base year for all items in theaggregate and dividing by the sum of the SLC price in the base year multiplied by production quantity for the base year for thesame items.
http://faostat3.fao.org/home/index.html#DOWNLOADGreyscale lines are countries not mentioned as having a riot in their chart, while the colored lines are the data from countries that did (if available). The dotted black line is the average of all countries, not just riot having countries.