National Interstate ( NATL) said earnings rose 21.9% from a year-ago period for the first quarter, thanks to an increase in premiums earned. The Richfield, Ohio-based insurance company earned $8.73 million, or 45 cents a share, in the quarter, compared with $7.16 million, or 39 cents a share, a year ago. Analysts surveyed by Thomson First Call were expecting earnings of 40 cents a share in the most recent quarter. First-quarter revenue rose 18.5% from a year ago to $55.1 million. Total premium earned increased 16.5% to $50.32 million and net investment income increased to $3.9 million from $2.67 million. Loss and loss adjustment expenses increased 14.7% to $29.9 million while loss and loss adjustment expense ratio decreased 100 basis points to 59.4%. Underwriting expense ratio increased 180 basis points to 22% and combined ratio stood at 81.4%. Gross premium written increased 5.8% to $109.54 million and net premium written increased 7.9% to $79.41. This lower growth rate is due to a portion of a large group captive program that renews in the first quarter of each year was moved to a new program that will renew in the fourth quarter. "Our continued strong profitability reflects our focus on risk selection, disciplined underwriting and our growing investment portfolio," the company said. "We are also pleased with our rate of premium growth given current market conditions."