The lenders in the combined residential mortgage market who control the MI decision are currently comprised of three groups:
Going forward, by April 15th of each year, NMIC must certify it met all PMIERs requirements as of December 31st of the prior year. Moreover, NMIC has an ongoing obligation to immediately notify the GSEs in writing upon discovery of its failure to meet one or more of the PMIERs requirements. We will continue to monitor our compliance with the PMIERs going forward.
In addition to GSE-imposed capital requirements, NMIC is also subject to state regulatory minimum capital requirements based on its insured RIF. While formulations of this minimum capital may vary in each jurisdiction, the most common measure allows for a maximum permitted RTC ratio of 25:1. As our insurance writings grow and our RIF increases, our RTC ratio will increase and NMIC's RTC metrics will become more important to an evaluation of its capital needs to support future business writings.
In April 2013, NMIC, our primary insurance subsidiary, issued its first mortgage insurance policy. NMIC is licensed to write mortgage insurance in all 50 states and D.C. In August 2015, NMIH capitalized with $0.5 million a wholly owned subsidiary, NMIS, through which we began to offer outsourced loan review services to mortgage loan originators in the fourth quarter of 2015.
Purchases and sales of investments are recorded on a trade date basis. Net investment income is recognized when earned and includes interest and dividend income together with amortization of market premiums and discounts using the effective yield method, and is net of investment management fees and other investment related expenses. For asset-backed securities and any other holdings for which there is a prepayment risk, prepayment assumptions are evaluated and revised as necessary. Any adjustments required due to the change in effective yields and maturities are recognized on a prospective basis through yield adjustments.
We consider items such as certificates of deposit and money market funds with original maturities of 90 days or less to be cash equivalents.
Goodwill represents the excess of the purchase price over the estimated fair value of net assets acquired from a business combination. In accordance with ASC 350, Intangibles - Goodwill and Other, we test goodwill for impairment during the third quarter each year, or more frequently if we believe indicators of impairment exist. We have not identified any impairments of goodwill through December 31, 2015.
The 2012 Stock Incentive Plan (Plan) was approved by the Board on April 16, 2012 and authorized 5.5 million shares to be reserved for issuance under the Plan, with 3.85 million shares available for stock options and 1.65 million shares available for RSUs. Options granted under the Plan are non-qualified stock options and may be granted to employees, directors and other key persons. The exercise price per share for the common stock covered by this Plan shall be determined by the Board at the time of grant, but shall not be less than the fair market value, defined as the closing price of our common stock, on the date of the grant. The term of the stock option grants will be established by the Board, but no stock option shall be exercisable more than ten years after the date the stock option is granted. The vesting period of the stock option grants will also be established by the Board at the time of grant and generally is for a three-year period. Upon the exercise of stock options, we issue shares from the authorized, unissued share reserve.
The remaining weighted average contractual life of non-vested RSUs as of December 31, 2015 was 8.06 years. The weighted-average period over which total compensation related to non-vested RSUs will be recognized is 1.44 years years.
As of December 31, 2015, the Company had a federal NOL of $139.4 million which expires from 2029 to 2035, and a state NOL of $47.0 million, which expires from 2031 to 2035. Section 382 of the Internal Revenue Code imposes annual limitations on a corporation's ability to utilize its net operating loss carryforwards if it experiences an "ownership change." As a result of the acquisition of our insurance subsidiaries, $7.3 million of NOLs are subject to annual limitations of $0.8 million through 2016, then $0.3 million through 2029.
as of December 31st of the prior year. Moreover, NMIC has an ongoing obligation to immediately notify the GSEs in writing upon discovery of its failure to meet one or more of the PMIERs requirements. We will continue to monitor our compliance with the PMIERs going forward.