1) The document describes a field experiment that randomized offers of index insurance to agricultural households in India to study the interaction between formal insurance and informal risk-sharing networks.
2) It finds that the presence of strong informal risk-sharing networks through castes/jatis reduces demand for formal insurance, and that basis risk, where payouts do not perfectly correlate with losses, also reduces demand.
3) However, informal and formal insurance can be complements when basis risk is high, as both provide partial coverage against different risks. The study uses detailed survey and rainfall data on castes/jatis to characterize their risk-sharing practices.