Knight-Swift Transportation Holdings Inc.          KNX,         -0.62%        said Friday it raised its quarterly dividend by 20%, to 12 cents a share from 10 cents. The freight transportation company’s new dividend will be payable March 28 to shareholders of record on March 4. Based on Thursday’s stock closing price of $56.74, the new annual dividend rate implies a dividend yield of 0.85%, which compares with the implied yield for the S&P 500          SPX,         +0.12%        of 1.40%. Knight-Swift’s stock, which was still inactive in premarket trading, has slipped 4.0% over the past three months, while the Dow Jones Transportation Average          DJT,         -1.22%        has declined 7.6% and the S&P 500 has eased 4.3%.