9. CONVERTIBLE NOTES, NET

As of December 31, 2018, the following convertible senior notes, or Convertible Notes, were outstanding ($ in thousands):


Convertible Notes Issuance	Face Value		Coupon Rate			All-in Cost⁽¹⁾			Conversion Rate⁽²⁾		Maturity
May 2017	$	402,500		4.38	%		4.85	%		28.0324	May 5, 2022
March 2018	$	220,000		4.75	%		5.33	%		27.6052	March 15, 2023

(1)	Includes issuance costs that are amortized through interest expense over the life of the Convertible Notes using the effective interest method.

(2)

Represents the shares of class A common stock per $1,000 principal amount of Convertible Notes, which is equivalent to a conversion price of $35.67 and $36.23 per share of class A common stock, respectively, for the May 2017 and March 2018 convertible notes. The cumulative dividend threshold as defined in the respective May 2017 and March 2018 convertible notes supplemental indentures have not been exceeded as of December 31, 2018.

The Convertible Notes are convertible at the holders’ option into shares of our class A common stock, only under specific circumstances, prior to the close of business on January 31, 2022 and December 14, 2022 for the May 2017 and March 2018 convertible notes, respectively, at the applicable conversion rate in effect on the conversion date. Thereafter, the Convertible Notes are convertible at the option of the holder at any time until the second scheduled trading day immediately preceding the maturity date. We may not redeem the Convertible Notes prior to maturity. The last reported sale price of our class A common stock of $31.86 on December 31, 2018 was less than the per share conversion price of the May 2017 and March 2018 convertible notes. We have the intent and ability to settle each series of the Convertible Notes in cash and, as a result, the Convertible Notes did not have any impact on our diluted earnings per share. During the year ended December 31, 2018, we settled $172.5 million of our convertible notes from our November 2013 issuance. The convertible notes were settled entirely in cash for an aggregate $219.2 million, resulting in a $46.7 million charge to our additional paid-in capital.

Upon our issuance of the November 2013 convertible notes, we recorded a $9.1 million discount based on the implied value of the conversion option and an assumed effective interest rate of 6.50%, as well as $4.1 million of initial issuance costs. Including the amortization of this discount and the issuance costs, our total cost of the November 2013 convertible notes issuance was 7.16% per annum. Our November 2013 convertible notes matured on December 1, 2018.

Upon our issuance of the May 2017 convertible notes, we recorded a $979,000 discount based on the implied value of the conversion option and an assumed effective interest rate of 4.57%, as well as $8.4 million of initial debt discount and issuance costs. Including the amortization of the discount and issuance costs, our total cost of the May 2017 convertible notes issuance is 4.91% per annum.

Upon our issuance of the March 2018 convertible notes, we recorded a $1.5 million discount based on the implied value of the conversion option and an assumed effective interest rate of 5.25%, as well as $5.2 million of initial debt discount and issuance costs. Including the amortization of the discount and issuance costs, our total cost of the March 2018 convertible notes issuance is 5.49% per annum.

The following table details the net book value of our Convertible Notes on our consolidated balance sheets ($ in thousands):


	December 31, 2018			December 31, 2017
Face value	$	622,500		$	575,000
Unamortized discount		(11,740	)		(10,279	)
Deferred financing costs		(849	)		(810	)

Net book value	$	609,911		$	563,911

The following table details our interest expense related to the Convertible Notes ($ in thousands):


	Year Ended December 31,
	2018		2017		2016
Cash coupon	$	33,859	$	19,259	$	9,056
Discount and issuance cost amortization		5,531		4,040		2,736

Total interest expense	$	39,390	$	23,299	$	11,792

Accrued interest payable for the Convertible Notes was $6.0 million and $3.7 million as of December 31, 2018 and December 31, 2017, respectively. Refer to Note 2 for additional discussion of our accounting policies for the Convertible Notes.