The following table summarizes the change in fair value of the Level 3 liabilities with significant unobservable inputs (in thousands):
The money market accounts are included in our cash and cash equivalents in our consolidated balance sheets. Our money market assets are valued using quoted prices in active markets.
The liability for the subsidiary unit awards relates to agreements established with employees of our subsidiaries for cash awards contingent upon the subsidiary companies meeting certain financial milestones such as revenue, working capital, EBITDA and EBITDA margin. We account for these subsidiary awards using fair value and establish liabilities for the future payment for the repurchase of subsidiary units under the terms of the agreements based on estimating revenue, working capital, EBITDA and EBITDA margin of the subsidiary units over the periods of the awards through the anticipated repurchase dates. We estimated the fair value of each liability by using a Monte Carlo simulation model for determining each of the projected measures by using an expected distribution of potential outcomes. The fair value of each liability is calculated with thousands of projected outcomes, the results of which are averaged and then discounted to estimate the present value. At each reporting date until the respective payment dates, we will remeasure these liabilities, using the same valuation approach based on the applicable subsidiary's revenue and future collection of financed customer receivables, the unobservable inputs, and we will record any changes in the employee's compensation expense. Some of the awards are subject to the employees' continued employment and therefore, recorded on a straight-line basis over the remaining service period. During the year ended December 31, 2019, we settled $0.2 million of the liability related to the subsidiary unit awards. The remaining liability balances are included in either accounts payable, accrued expenses and other current liabilities or other liabilities in our consolidated balance sheets (see Note 13).
The contingent consideration liability consists of the potential earn-out payment related to our acquisition of 85% of the issued and outstanding capital stock of OpenEye on October 21, 2019. The earn-out payment is contingent on the satisfaction of certain calendar 2020 revenue targets and has a maximum potential payment of up to $11.0 million. We account for the contingent consideration using fair value and establish a liability for the future earn-out payment based on an estimation of revenue attributable to perpetual licenses and subscription licenses over the 2020 calendar year. We estimated the fair value of the liability by using a Monte Carlo simulation model for determining each of the projected measures by using an expected distribution of potential outcomes. The contingent consideration liability was valued with Level 3 unobservable inputs, including the revenue volatility and the discount rate. At October 21, 2019, the fair value of the liability was $2.8 million. At each reporting date until the payment date in 2021, we will remeasure the liability, using the same valuation approach. Changes in the fair value resulting from information that existed subsequent to the acquisition date are recorded in the consolidated statements of operations. During the year ended December 31, 2019, the contingent consideration liability decreased $0.2 million to $2.6 million as compared to the initial liability recorded at the acquisition date, primarily due to a change to OpenEye's 2020 projected revenue. The unobservable inputs used in the valuation as of December 31, 2019 included a revenue volatility of 45% and a discount rate of 3%. Selecting another revenue volatility or discount rate within an acceptable range would not result in a significant change to the fair value of the contingent consideration liability.
The contingent consideration liability is included in other liabilities in our consolidated balance sheet as of December 31, 2019 (see Note 13).
We monitor the availability of observable market data to assess the appropriate classification of financial instruments within the fair value hierarchy. Changes in economic conditions or model-based valuation techniques may require the transfer of financial instruments from one fair value level to another. In such instances, the transfer is reported at the beginning of the reporting period. There were no transfers between Levels 1, 2 or 3 during the years ended December 31, 2019, 2018 and 2017. We also monitor the value of the investments for other-than-temporary impairment on a quarterly basis. No other-than-temporary impairments occurred during the years ended December 31, 2019, 2018 and 2017.
Table:
 | Fair Value Measurements Using Significant Unobservable Inputs |  | 
 | Year Ended December 31, 2019 |  | Year Ended December 31, 2018
 | Subsidiary Unit Awards | Contingent Consideration Liability from Acquisitions | Subsidiary Unit Awards
Beginning of period balance | 385 | $ — | $3,160
Acquired liabilities | — | 2,793 | —
Changes in fair value included in earnings | (14) | (198) | 27
Settlements | (200) | — | (2,802)
End of period balance | $171 | $2,595 | $385


Question: How many years did the beginning of period balance exceed $2,000 thousand?
Answer: 1
Calculation: 2018