Every life, fire and casualty, hail and county mutual fire insurance company organized under the laws of this state, shall annually pay to the state for the privilege of doing business within this state, a tax according to or measured by its net income for the next preceding calendar year. Such tax shall be an amount equal to five percent (5%) of such net income. The provisions of this section shall not apply to net income earned in calendar year 1998 or in any calendar year thereafter.