The risks insured in our medical technology liability business (3% of our consolidated gross reserve for losses and loss adjustment expenses as of December 31, 2019) are more varied, and policies are individually priced based on the risk characteristics of the policy and the account. The insured risks range from startup operations to large multinational entities, and the larger entities often have significant deductibles or self-insured retentions. Reserves are established using our most recently developed actuarial estimates of losses expected to be incurred based on factors which include results from prior analysis of similar business, industry indications, observed trends and judgment. Claims in this line of business primarily involve bodily injury to individuals and are affected by factors similar to those of our HCPL line of business. For the medical technology liability business, we also establish an initial reserve using a loss ratio approach, including a provision in consideration of historical loss volatility that this line of business has exhibited.
Segregated Portfolio Cell Reinsurance Segment. The factors that affect the ultimate losses incurred for the workers' compensation and healthcare professional liability coverages assumed by the SPCs at Inova Re and Eastern Re (4% of our consolidated gross reserve for losses and loss adjustment expenses as of December 31, 2019) are consistent with that of our Workers’ Compensation Insurance and Specialty P&C segments, respectively.
The acquisition of Eastern on January 1, 2014 increased our loss reserve by $153.2 million which represented the fair value of Eastern's loss reserve at the time of the acquisition. The fair value of the reserve for losses and loss adjustment expenses and related reinsurance recoverables was based on an actuarial estimate of the expected future net cash flows, a reduction of those cash flows for the time value of money determined utilizing the U.S. Treasury Yield Curve, and a risk adjustment to reflect the net present value of profit that an investor would demand in return for the assumption of the associated risks. Expected net cash flows were derived from the expected loss payment patterns included in an actuarial analysis of Eastern's reserve performed as of December 31, 2013. The fair value of the reserve, including the risk margin discussed above, exceeded the undiscounted loss reserve previously established by Eastern by $9.3 million; this fair value adjustment was amortized over the average expected life of the reserve of 6 years. The fair value adjustment has been fully amortized as of December 31, 2019.
subjective process that is inherently likely to prove inaccurate over time. Given the long tail and volatility, we are generally cautious in making changes to the severity assumptions within our pricing models. All open claims and accident years are generally impacted by a change in the severity trend, which compounds the effect of such a change.
Catastrophic protection is utilized on both our property insurance and casualty coverages to protect against losses in excess of policy limits as well as natural catastrophes.
A detailed listing of our investment holdings as of December 31, 2019 is located under the Financial Information heading on the Investor Relations page of our website which can be reached directly at www.proassurance.com/investmentholdings, or through links from the Investor Relations section of our website, investor.proassurance.com.
We have no significant off-balance sheet arrangements/guarantees that have or are reasonably likely to have a material current or future effect on our financial condition, changes in financial condition, revenues or expenses, results of operations, liquidity, capital expenditures or capital resources. See more information on our off-balance sheet arrangements in Note 9 of the Notes to Consolidated Financial Statements.
At December 31, 2019, there were no outstanding borrowings on our Revolving Credit Agreement; however, the above table includes unused commitment fees associated with our Revolving Credit Agreement as we presume the full unused facility will remain available through expiration of the agreement in November 2024. Additionally, we presume the current interest rate on our Mortgage Loans at December 31, 2019 will remain constant until maturity of the Mortgage Loans in December 2027. For more information regarding these agreements see Note 11 of the Notes to Consolidated Financial Statements.
2018 in our Specialty P&C segment (see further discussion in our Segment Operating Results - Specialty Property & Casualty section that follows). Excluding the impact of the 2018 loss portfolio transfer, our consolidated underwriting expense ratio for 2019 was relatively unchanged as compared to 2018 driven by an increase in consolidated net premiums earned which outpaced the increase in consolidated DPAC amortization, offset by an increase operating expenses in our Specialty P&C segment driven by fees associated with a data analytics services agreement entered into during the fourth quarter of 2018.
Our medical technology liability business is marketed throughout the U.S.; coverage is typically offered on a primary basis, within specified limits, to manufacturers and distributors of medical technology and life sciences products including entities conducting human clinical trials. In addition to the previously listed factors that affect our premium volume, our medical technology liability premium is impacted by the sales volume of insureds. The increase in 2019 was primarily due to new business written and, to a lesser extent, an increase in renewal pricing, largely offset by retention losses. Renewal pricing increases primarily reflect increases in the sales volume and exposure of certain insureds. Retention losses in 2019 are primarily attributable to an increase in competition on terms and pricing.
During 2019 and 2018, we increased the premiums owed under reinsurance agreements for prior accident years which decreased net premiums earned (the denominator of the current accident year ratio). See the discussion in the Premiums section for our Specialty P&C segment under the heading "Ceded Premiums Written" for additional information.
A detailed discussion of factors influencing our recognition of loss development is included in our Critical Accounting Estimates section under the heading "Reserve for Losses and Loss Adjustment Expenses." Assumptions used in establishing our reserve are regularly reviewed and updated by management as new data becomes available. Any adjustments necessary are reflected in the then current operations. Due to the size of our reserve, even a small percentage adjustment to the assumptions can have a material effect on our results of operations for the period in which the change is made, as was the case in both 2019 and 2018.
Calendar year incurred losses (excluding IBNR) ceded to our external reinsurers decreased $10.1 million for the year ended December 31, 2019 as compared to 2018. Current accident year ceded incurred losses decreased $5.5 million as compared to 2018. The decrease in losses ceded to our external reinsurers primarily reflects the impact of the AAD, which reduced ceded losses by $3.9 million, and a reduction in reported reinsured claims during 2019.
For the workers' compensation business, each SPC has in place its own external reinsurance arrangements. The healthcare professional liability business is assumed net of reinsurance from our Specialty P&C segment; therefore, there are no ceded premiums related to the healthcare professional liability business reflected in the table above. The risk retention for each loss occurrence for the workers' compensation business ranges from $0.3 million to $0.35 million based on the program, with limits up to $119.7 million. In addition, each program has aggregate reinsurance coverage between $1.1 million and $2.1 million on a program year basis. Per the SPC external reinsurance agreements, premiums are ceded on a written premium basis and changes in ceded premiums written during 2019 primarily reflected changes in gross premiums written as compared to 2018. External reinsurance rates vary based on the alternative market program.
In addition to the results of our participation in Lloyd's Syndicates, as discussed above, our Lloyd's Syndicates segment also includes 100% of the operating results of our wholly owned subsidiaries that support our operations at Lloyd's. For the years ended December 31, 2019 and 2018, the results of our Lloyd's Syndicates segment were as follows: