What affects the industrial production index?

The Industrial Production Index gets affected by inward factors such as imports, expenditure, consumptions, and public expenditure. The Industrial Production Index also gets affected by outward factors such as export, exchange rate, and oil prices. You can read about the Index of Industrial Production [UPSC Economy Notes] in the given link.

The eight core industries of India represent about 40% of the weight of items that are included in the IIP.

Further readings:

1. Merger of NSSO and Central Statistical Office (CSO) to form National Statistical Office (NSO)
2. Core Sectors of the Indian Economy