The Company has two classes of common stock: class A common stock and class B common stock. Holders of class A common stock generally have the same rights, including rights to dividends, as holders of class B common stock, except that holders of class A common stock have one vote per share while holders of class B common stock have 10 votes per share. Each share of class B common stock is convertible at any time, at the option of the holder, into one share of class A common stock. As such, basic and fully diluted earnings per share for class A common stock and for class B common stock are the same. The Company has never declared or paid any cash dividends on either class A or class B common stock. As of September 30, 2021 and December 31, 2020, there were no shares of preferred stock issued or outstanding.

Potential shares of common stock are included in the diluted earnings per share calculation when dilutive. Potential shares of class A common stock issuable upon the exercise of outstanding stock options, the vesting of outstanding restricted stock units, and in connection with the 2021 ESPP are calculated using the treasury stock method. Potential shares of class A common stock issuable upon conversion of the Convertible Notes are calculated using the if-converted method. In computing diluted earnings per share, the Company first calculates the earnings per incremental share (“EPIS”) for each class of potential common shares and ranks the classes from the most dilutive (i.e., lowest EPIS) to the least dilutive (i.e., highest EPIS). Basic earnings per share is then adjusted for the effect of each class of shares, in sequence and cumulatively, until a particular class no longer produces further dilution.

For the three and nine months ended September 30, 2021 and 2020, the following weighted average shares of potential class A common stock were excluded from the diluted loss per share calculation because their impact would have been anti-dilutive (in thousands):

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2021		2020		2021		2020
Stock Options		1,252		1,476		1,246		1,536
Restricted Stock Units		103		0		91		0
Employee Stock Purchase Plan		2		0		1		0
2025 Convertible Notes		1,633		0		1,633		0
2027 Convertible Notes		733		0		601		0
Total		3,723		1,476		3,572		1,536

On June 14, 2021, the Company entered into an Open Market Sale Agreement (the “Sale Agreement”) with Jefferies LLC, as agent (“Jefferies”), pursuant to which the Company may issue and sell shares of its class A common stock having an aggregate offering price of up to $1.0 billion from time to time through Jefferies (the “Open Market Offering”).

Under the Sale Agreement, any sales of shares will be made by methods deemed to be an “at-the-market offering” as defined in Rule 415(a)(4) promulgated under the Securities Act of 1933, as amended. Any sales of shares under the Sale Agreement will be made in amounts and at times to be determined by the Company from time to time subject to the terms and conditions of the Sale Agreement, but the Company has no obligation to sell any of the shares in an Open Market Offering.

The Company or Jefferies may suspend or terminate the Open Market Offering upon notice to the other party and subject to other conditions. The Company has agreed to pay Jefferies commissions for its services in acting as agent in the sale of the shares in the amount of up to 2.0% of gross proceeds from the sale of shares pursuant to the Sale Agreement. The Company has also agreed to provide Jefferies with customary indemnification and contribution rights.

During the three and nine months ended September 30, 2021 the Company issued and sold 555,179 shares of its class A common stock under the Sale Agreement, at an average gross price per share of approximately $727.64, for aggregate net proceeds (less $4.5 million in sales commissions and expenses) of approximately $399.5 million. The sales commissions and expenses related to the Sale Agreement are considered direct and incremental costs and are charged against “Additional paid-in capital” on the balance sheet in the period in

which the related shares are issued and sold. As of September 30, 2021, approximately $596.0 million of the Company’s class A common stock remained available for issuance and sale pursuant to the Sale Agreement.