Share-based compensation
We follow ASC 718 to determine whether a share option or a restricted share unit should be classified and accounted for as a liability award or equity award. All grants of share-based awards to employees and directors classified as equity awards are recognized in the financial statements based on their grant-date fair values which are calculated using an option pricing model. We classify the share-based awards granted to employees as equity awards, and have elected to recognize compensation expense relating to the share-based awards with service condition on a graded vesting basis over the requisite service period, which is generally the vesting period.
Under ASC 718, we apply the Binomial option pricing model in determining the fair value of options granted. ASC 718 requires forfeiture rates to be estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from initial estimates. Share-based compensation expense is recorded net of estimated forfeitures such that expense is recorded only for those share-based awards that are expected to vest.
In February 2018, we adopted the Amended and Restated Plan, which was later amended and renamed as the 2018 Second Amended and Restated Share Incentive Plan (the “Amended and Restated Plan”). Under the Amended and Restated Plan, the maximum aggregate number of Class A ordinary shares that may be issued pursuant to all awards granted under the Amended and Restated Plan is 102,040,053.
On September 22, 2019, our board of directors approved a reduction in the exercise price for outstanding options previously granted by our company with an exercise price higher than $1.03 per ordinary share, up to US$3.00 per ordinary share, to $1.03 per share, provided that any participating option holder agrees to amendment in the number of shares subject to his or her option as determined by the plan administrator. We accounted for this reduction as a share option modification which required the remeasurement of these share options at the time of the modification. The total incremental cost as a result of the modification was US$4.1 million. The incremental cost related to vested options amounted to US$2.1 million and was recorded in the consolidated statements of comprehensive loss during the year ended December 31, 2019. The incremental cost related to unvested options amounted to US$2.0 million and will be recorded over the remaining service period.
Options
We granted 12,819,330, 25,224,000, 4,247,500 and 2,175,300 options to our employees, with a weighted average exercise price of US$2.13, US$2.90, US$1.36 and US$0.03, for the years ended December 31, 2017, 2018, 2019 and the three months ended March 31, 2020, respectively. No options granted to employees were exercisable as of December 31 2017, whereas 18,659,232, 19,698,819 and 21,373,800 options were exercisable as of December 31, 2018 and 2019 and March 31, 2020, respectively. 9,800,000, 7,300,000, 10,570,575 and 13,234,329 options granted to key management became exercisable as of December 31, 2017, 2018 and 2019 and March 31, 2020, respectively.
Under the Amended and Restated Plan, employees are generally subject to a four-year service schedule, under which an employee earns an entitlement to vest in 25% of his or her option grants at the end of each year of completed service.
As of March 31, 2020, the fair value of vested and nonvested options granted to employees and management amounted to RMB39.2 million (US$5.5 million) and RMB18.0 million (US$2.5 million), respectively, and a share-based compensation expense of RMB32.1 million (US$4.5 million) was recognized for the vested options.
Other share-based awards
For the year ended December 31, 2016, we recorded share-based compensation expense of RMB226.4 million for issuance and grant of 19,985,520 ordinary shares to our management in April 2016.
In September 2017, one of our preferred shareholders transferred 6,686,020 series A preferred shares and 10,590,390 series B preferred shares with a consideration of US$41.2 million to Gao Li Group, which is controlled by Mr. Kun Dai, the chairman of our board of directors and chief executive officer. The difference between the transfer price and the fair value of preferred shares transferred was RMB137.7 million and was recognized as compensation expense to Mr. Kun Dai in September 2017.
In June 2018, we recorded share-based compensation expense of RMB620.4 million for the issuance of 17,742,890 restricted shares to Mr. Kun Dai, which were vested immediately upon consummation of a successful initial public offering.