Shares of AMERISAFE (NASDAQ: AMSF), an insurance company focused on providing workers compensation insurance to small- and mid-sized businesses, tumbled as much as 13% on Thursday after reporting its first-quarter earnings results during the after-hours trading session on Wednesday.As you can probably guess from the substantial move lower, AMERISAFE's quarterly profit results came nowhere near what the Street had been forecasting for Q1.For the quarter, AMERISAFE recorded $90.9 million in net premiums earned, representing a 5% year-on-year decline and $6.7 million in investment income, which was an 11% increase from the prior-year quarter.