Explanation:

WPI is average price changes of goods that are traded in the wholesale market.
It is a weekly measure of wholesale price movement of the economy. 
It includes only the prices of goods and does not include items pertaining to services. 
In India, WPI is published by the Office of Economic Adviser, Ministry of Commerce and Industry weekly. 
It has a time lag of two weeks.
Items Included in Wholesale Price Index
There are 697 items are included in the index. These items are further divided into three categories:
Primary articles: The Primary articles are food items, non-food items and minerals. There are 117 items for Primary Articles.
Fuel and Power: It includes power, light and lubricants, electricity, coal mining and mineral oil. There are 16 items for Fuel & Power.
Manufactured Goods: It includes food products, beverages, tobacco and tobacco products, wood and wood products, textiles, paper and paper products, basic metals, alloys, rubber and rubber products etc. There are 564 items for Manufactured Products.