On June 1, 2020, employees were granted the right to purchase an aggregate of 58,096 shares under the ESPP, and compensation expense related to those purchase rights for the nine months ended March 31, 2021 was $169,000.
On December 1, 2020, employees were granted the right to purchase an aggregate of 74,752 shares under the ESPP, and compensation expense related to those purchase rights for the three and nine months ended March 31, 2021 was $185,000.
On December 1, 2019, employees were granted the right to purchase an aggregate of 69,368 shares under the ESPP, and compensation expense related to those purchase rights for the three and nine months ended March 31, 2020 was $87,000.
As of March 31, 2021, there were 716,122 shares of common stock available for issuance under the ESPP.
We base our estimate of expected life of a stock option on the historical exercise behavior and cancellations of all past option grants made by the Company during the time period which its equity shares have been publicly traded, the contractual term of the option, the vesting period and the expected remaining term of the outstanding options.
In accordance with ASU 2016-09, Compensation—Stock Compensation: Improvements to Employee Share-Based Accounting, we elected to continue to estimate forfeitures in the calculation of stock-based compensation expense.
As of March 31, 2021 there was approximately $1.2 million of total unrecognized compensation cost related to nonvested stock options, which is expected to be recognized over the weighted-average period of 1.2 years. There were 43,796 and 52,004 options exercised during the three months ended March 31, 2021 and 2020, respectively. There were 213,850 and 141,639 options exercised during the nine months ended March 31, 2021 and 2020, respectively.
Leases
Lease agreements are evaluated to determine whether an arrangement is or contains a lease in accordance with ASC 842, Leases.
Operating leases are included in operating lease right-of-use (ROU) assets, current operating lease liabilities, and noncurrent operating lease liabilities in the condensed consolidated financial statements. ROU assets represent the Company’s right to use leased assets over the agreed upon term. Lease liabilities represent the Company’s contractual obligation to make lease payments over the lease term.
For operating leases, ROU assets and lease liabilities are recognized at the commencement date of the lease. The lease liability is measured as the present value of the lease payments over the lease term, using the rate implicit in the lease if readily determinable. If the rate implicit in the lease cannot be readily determined, the Company uses its incremental borrowing rate at lease commencement. The operating lease right-of-use assets are calculated as the present value of the remaining lease payments plus unamortized initial direct costs and any prepayments, less unamortized lease incentives received.
Operating leases typically include non-lease components such as common-area maintenance costs. We have elected to include non-lease components with lease payments for the purpose of calculating lease right-of-use assets and liabilities, to the extent that they are fixed. Non-lease component payments that are not fixed are expensed as incurred as variable lease payments.
Lease terms may include renewal or extension options to the extent they are reasonably certain to be exercised. The assessment of whether renewal or extension options are reasonably certain to be exercised is made at lease commencement. Factors considered in determining whether an option is reasonably certain of exercise include, but are not limited to, the value of any leasehold improvements, the value of renewal rates compared to market rates, and the presence of factors that would cause a significant economic penalty to the Company if the option were not exercised. Lease expense is recognized on a straight-line basis over the lease term. The Company has elected not to recognize right-of-use assets and obligations for leases with an initial term of twelve months or less, and has applied a capitalization threshold to recognize a lease on