Residential Mortgage Servicing Rights

The following table presents the changes in the Company's residential mortgage servicing rights ("MSR") for the years ended December 31, 2014, 2013 and 2012:



(in thousands)	2014			2013			2012
Balance, beginning of period	$	47,765		$	27,428		$	18,184
Acquired/purchased MSR	62,770			—			—
Additions for new MSR capitalized	23,311			17,963			17,710
Changes in fair value:
Due to changes in model inputs or assumptions(1)	(5,757		)	5,688			(4,651		)
Other(2)	(10,830		)	(3,314		)	(3,815		)
Balance, end of period	$	117,259		$	47,765		$	27,428


(1)	Principally reflects changes in discount rates and prepayment speed assumptions, which are primarily affected by changes in interest rates.


(2)	Represents changes due to collection/realization of expected cash flows over time.

Information related to our serviced loan portfolio as of December 31, 2014, 2013 and 2012 is as follows:



(dollars in thousands)	December 31, 2014			December 31, 2013			December 31, 2012
Balance of loans serviced for others	$	11,590,310		$	4,362,499		$	3,162,080
MSR as a percentage of serviced loans	1.01		%	1.09		%	0.87		%

The amount of contractually specified servicing fees, late fees and ancillary fees earned, recorded in residential mortgage banking revenue on the Consolidated Statements of Income, was $20.8 million, $10.4 million, and $6.6 million for the years ended December 31, 2014, 2013 and 2012.

Key assumptions used in measuring the fair value of MSR as of December 31 were as follows:



	2014		2013		2012
Constant prepayment rate	12.39	%	12.74	%	21.39	%
Discount rate	9.17	%	8.69	%	8.65	%
Weighted average life (years)	6.4		6.0		4.7

A sensitivity analysis of the current fair value to changes in discount and prepayment speed assumptions as of December 31, 2014 and December 31, 2013 is as follows:



	December 31, 2014			December 31, 2013
Constant prepayment rate
Effect on fair value of a 10% adverse change	$	(4,965	)	$	(2,255	)
Effect on fair value of a 20% adverse change	$	(9,547	)	$	(4,323	)

Discount rate
Effect on fair value of a 100 basis point adverse change	$	(4,539	)	$	(1,832	)
Effect on fair value of a 200 basis point adverse change	$	(8,771	)	$	(3,534	)

The sensitivity analysis presents the hypothetical effect on fair value of the MSR. The effect of such hypothetical change in assumptions generally cannot be extrapolated because the relationship of the change in an assumption to the change in fair value is not linear. Additionally, in the analysis, the impact of an adverse change in one assumption is calculated independent of any impact on other assumptions. In reality, changes in one assumption may change another assumption.