Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

Federal taxes for nonresident alien whose only income in 2016 was a 2015 state tax return
I believe you have to file a tax return, because state tax refund is considered income effectively connected with US trade or business, and the 1040NR instructions section "Who Must File" includes people who were engaged in trade or business in the US and had a gross income. You won't end up having to pay any taxes as the income is less than your personal exemption of $4050.