Health Insurance Innovations Inc. saw the biggest decrease in short interest relative to shares outstanding among SNL-covered insurance companies between Dec. 30, 2016, and Jan. 13.

The percentage of the company's shares held short relative to shares outstanding declined 112 basis points to 13.34% as of Jan. 13.

Ambac Financial Group Inc. topped the list of insurance companies with the biggest gains in short interest in the first half of January. The company saw short interest rise 107 basis points to 4.56% of shares outstanding at the end of the period.

Molina Healthcare Inc. topped the list of most shorted insurance companies in the first half of January. The company saw short interest climb 2 basis points to 15.13% of shares outstanding.