The following table presents changes in mortgage servicing rights for the periods presented:


(dollars in thousands)	Mortgage Servicing Rights
Balance, January 1, 2019	$	15,596
Additions	742
Amortization	(1,072)
Balance, June 30, 2019	$	15,266

Balance, January 1, 2020	$	14,718
Additions	1,270
Amortization	(3,217)
Balance, June 30, 2020	$	12,771

Income generated as the result of new mortgage servicing rights is reported as gains on sales of loans and totaled $1.1 million and $1.3 million for the three and six months ended June 30, 2020 compared to $0.5 million and $0.7 million for the three and six months ended June 30, 2019.

Amortization of mortgage servicing rights totaled $1.7 million and $3.2 million for the three and six months ended June 30, 2020 compared to $0.6 million and $1.1 million for the three and six months ended June 30, 2019.

The following tables present the fair market value and key assumptions used in determining the fair market value of our mortgage servicing rights:


	Six Months Ended		Six Months Ended
(dollars in thousands)	June 30, 2020		June 30, 2019
Fair market value, beginning of period	$	15,820	$	17,696
Fair market value, end of period	13,060		15,554


	June 30, 2020		December 31, 2019
Weighted average discount rate	9.6	%	9.5	%
Forecasted constant prepayment rate assumption ⁽¹⁾	21.7	%	11.9	%

⁽¹⁾ Represents annualized loan prepayment rate assumption.

The gross carrying value and accumulated amortization related to our mortgage servicing rights are presented below:


	June 30, 2020										December 31, 2019
(dollars in thousands)	Gross Carrying Value		Accumulated Amortization		Net Carrying Value		Gross Carrying Value		Accumulated Amortization		Net Carrying Value

Mortgage servicing rights	$	68,865	$	(56,094)	$	12,771	$	67,595	$	(52,877)	$	14,718

Based on the mortgage servicing rights held as of June 30, 2020, estimated amortization expense for the remainder of fiscal year 2020, the next five succeeding fiscal years and all years thereafter are as follows (dollars in thousands):


Year Ending December 31,
2020 (remainder)	$	2,583
2021	4,359
2022	3,538
2023	2,291
2024	—
2025	—
Thereafter	—
Total	$	12,771