If the severity trend were to be higher by 1 percentage point, the impact would be an increase in our initial expected loss ratio for this business of 3.2 percentage points, based on current claim disposition patterns. An increase in the severity trend of 3 percentage points would result in a 10.1 percentage point increase in our initial expected loss ratio. Due to the long-tailed nature of our claims and the previously discussed historical volatility of loss costs, selection of a severity trend assumption is a
In 2019, 2018 and 2017 the development was largely attributable to favorable results from claims closed during the year. As time has elapsed we have recognized that actual loss experience has on average been better than estimated. We have been cautious in recognizing the improvement, but as claims have matured and claims are closed or have become more certain for the remaining open claims, we have revised reserve estimates. We believe the need for a cautious approach is required as outcomes are uncertain and results can be significantly affected by outcomes for a small number of cases.
Both quota share reinsurance and excess of loss reinsurance are utilized to manage the net loss exposure on our property reinsurance coverages.
During 2019, we recognized OTTI in earnings of $0.8 million and non-credit OTTI in OCI of $0.2 million, both of which related to three corporate bonds in the energy and consumer sectors. We recognized OTTI in earnings of $0.5 million during 2018 related to debt instruments from two issuers in the energy sector. Other net realized investment gains during 2019 was driven by changes in the fair value of our equity trading portfolio. See further discussion in our Segment Operating Results - Corporate section that follows.
(1) Net realized investment gains (losses) on investments related to SPCs are recognized in our Segregated Portfolio Cell Reinsurance segment. SPC operating results, including any realized gain or loss, that are attributable to external cell participants are reflected in the SPC dividend expense (income). To be consistent with our exclusion of net realized investment gains (losses) recognized in earnings, we are excluding the portion of net realized investment gains (losses) that is included in the SPC dividend expense (income) which is attributable to the external cell participants.
We offer custom alternative risk solutions including loss portfolio transfers for healthcare entities that, most commonly, are exiting a line of business, changing an insurance approach or simply preferring to transfer risk. In the third quarter of 2019, we entered into a loss portfolio transfer with a regional hospital group which resulted in $0.9 million of retroactive premium written and fully earned in 2019. In the second quarter of 2018, we entered into a loss portfolio transfer with a large healthcare organization which resulted in $18.7 million of retroactive premium written and fully earned in 2018. See Note 4 of the Notes to Consolidated Financial Statements for further information on these transactions.
The increase in our alternative market healthcare facilities premium during 2019 was primarily due to new business written, including the addition of one large policy totaling $1.4 million. The remaining increase was attributable to multiple short-term policies written throughout 2018 that renewed on January 1, 2019 with twelve month terms.
As previously discussed, as a part of our alternative market solutions, all or a portion of certain healthcare premium written is ceded to SPCs in our Segregated Portfolio Cell Reinsurance segment under either excess of loss or quota share reinsurance agreements, depending on the structure of the individual program. See the Segment Operating Results - Segregated Portfolio Cell Reinsurance section for further discussion on the cession to SPCs from our Specialty P&C segment. The increase in premiums ceded to SPCs during 2019 was primarily due to new business written and the renewal of multiple short-term policies written throughout 2018 that renewed on January 1, 2019 with twelve month terms (see discussion in footnote 8 under the heading "Gross Premiums Written").
Management fees are charged pursuant to a management agreement by the Corporate segment to the operating subsidiaries within our Specialty P&C segment for services provided based on the extent to which services are provided to the subsidiary and the amount of premium written by the subsidiary. While the terms of the management agreement were consistent between 2019 and 2018, fluctuations in the amount of premium written by each subsidiary can result in corresponding variations in the management fee charged to each subsidiary during a particular period.
The majority of premiums in our Segregated Portfolio Cell Reinsurance segment are assumed from either our Workers' Compensation Insurance or Specialty P&C segments. Premium volume is driven by five primary factors: (1) the amount of new business written, (2) retention of the existing book of business, (3) premium rates charged on the renewal book of business and, for workers' compensation business, (4) changes in payroll exposure and (5) audit premium.
Excluding the impact of the errors and omissions liability policy, as shown above, the current accident year net loss ratio increased in 2019 as compared to 2018 primarily due to an increase in severity-related claims activity.
Calendar year incurred losses ceded to our external reinsurers increased $11.1 million for the year ended December 31, 2019 as compared to 2018. Current accident year ceded incurred losses increased $9.1 million for the year ended December 31, 2019 as compared to 2018. The increase in current accident year ceded incurred losses primarily reflected the impact of four claims totaling $11.2 million, of which $8.3 million related to two claims, incurred in 2019.
Losses for the year were primarily recorded using the loss assumptions by risk category incorporated into the business plans submitted to Lloyd's for Syndicate 1729 and Syndicate 6131 with consideration given to loss experience incurred to date. The assumptions used in each business plan were consistent with loss results reflected in Lloyd's historical data for similar risks. The loss ratios may fluctuate due to the timing of earned premium adjustments (see discussion in this section under the heading "Net Premiums Earned"). Premium and exposure for some of Syndicate 1729's insurance policies and reinsurance contracts are initially estimated and subsequently adjusted over an extended period of time as underlying premium reports are received from cedants and insureds. When reports are received, the premium, exposure and corresponding loss estimates are revised accordingly. Changes in loss estimates due to premium or exposure fluctuations are incurred in the accident year in which the premium is earned.
Our tax credit partnership investments are designed to generate returns in the form of tax credits and tax-deductible project operating losses and are comprised of qualified affordable housing project tax credit partnerships and historic tax credit partnerships. We account for our tax credit partnership investments under the equity method and record our allocable portion of the operating losses of the underlying properties based on estimates provided by the partnerships. For our qualified affordable housing project tax credit partnerships, we adjust our estimates of our allocable portion of operating losses periodically as actual operating results of the underlying properties become available. Our historic tax credit partnerships are short-term in nature and the majority of the remaining operating losses are expected to be recognized in 2020. The results from our tax credit partnership investments for the year ended December 31, 2019 reflected lower partnership operating losses as compared to 2018. Based on operating results received, we increased our estimate of partnership operating losses by $3.0 million in each of the years ended December 31, 2019 and 2018.
Consolidated interest expense for the years ended December 31, 2019 and 2018 was comprised as follows: