NOTE 5. FINANCIAL INSTRUMENTS

Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The fair value hierarchy is based on three levels of inputs, the first two of which are considered observable and the last unobservable, that may be used to measure fair value, as follows:

The Company classifies its financial instruments within Level 1 or Level 2 of the fair value hierarchy on the basis of valuations using quoted market prices or alternate pricing sources and models utilizing market observable inputs, respectively. The Company’s money market funds are valued based on quoted prices for the specific securities in an active market and are therefore classified as Level 1. The Company’s government securities and corporate debt securities are valued on the basis of valuations provided by third-party pricing services, as derived from such services’ pricing models, and are therefore classified as Level 2. As of March 31, 2019, the Company has not made any adjustments to the prices obtained from its third-party pricing providers.

Cash and Cash Equivalents and Marketable Securities

The Company’s money market funds and marketable securities are categorized as Level 1 and 2, respectively, within the fair value hierarchy. The following table shows the cost, gross unrealized losses and fair value, with a breakdown by significant investment category, of the Company’s cash and cash equivalents and marketable securities as of March 31, 2019:

As of December 31, 2018, the Company’s cash and cash equivalents and marketable securities balances were as follows:

The following tables show information about the Company’s marketable securities that have been in a continuous unrealized loss position for less than 12 months and for 12 months or greater as of March 31, 2019 and December 31, 2018:

All marketable securities held by the Company as of March 31, 2019 will mature in one year or less.

The Company may sell certain of its marketable securities prior to their stated maturities for strategic reasons including, but not limited to, anticipation of credit deterioration and duration management. As of March 31, 2019, the Company considered the declines in market value of its marketable securities to be temporary in nature. The Company typically invests in highly-rated securities, and its investment policy generally limits the amounts that may be invested with any one issuer. The policy generally requires investments to be investment grade, with the primary objective of minimizing the potential risk of principal loss. Fair values were determined for each individual security in the securities portfolio.

There were no transfers between Level 1, Level 2 or Level 3 financial instruments in the three months ended March 31, 2019.

Stock Warrants

All of the Company’s outstanding stock warrants are categorized as Level 3 within the fair value hierarchy. Stock warrants have been recorded at their fair value using either a probability weighted expected return model or the Black-Scholes option-pricing model. These models incorporate contractual terms, maturity, risk-free interest rates and volatility. The value of the Company’s stock warrants would increase if a higher risk-free interest rate was used, and would decrease if a lower risk-free interest rate was used. Similarly, a higher volatility assumption would increase the value of the stock warrants, and a lower volatility assumption would decrease the value of the stock warrants. The development and determination of the unobservable inputs for Level 3 fair value measurements and fair value calculations are the responsibility of the Company’s management with the assistance of a third-party valuation specialist.

In April 2018, in connection with the advisory agreement between the Company and a financial advisory firm, the Company issued such firm a five-year warrant to purchase up to 20,000 shares of the Company’s common stock (“April 2018 Warrant”). The April 2018 Warrant was fully vested and exercisable upon issuance and has an exercise price of $11.73 per share. The Company recorded this stock warrant at its fair value using the Black-Scholes option-pricing model. The holder is able to redeem the warrant for a number of shares having a value equal to the in-the-money value of the warrant. The Company recorded the fair value of the warrant as a liability upon issuance, and such fair value is remeasured as of the end of each reporting period. The April 2018 Warrant was outstanding at March 31, 2019.

The following table summarizes quantitative information with respect to the significant unobservable inputs that were used to value the April 2018 Warrant:

The following table represents a roll-forward of the fair value of the April 2018 Warrant, which was recorded within other accrued liabilities in the accompanying condensed consolidated balance sheet at March 31, 2019 :

The adjustment to the fair value of the April 2018 Warrant was recorded in other income, net in the Company’s consolidated statement of operations and comprehensive loss for the three months ended March 31, 2019.