Catastrophe losses is a commonly used non-GAAP financial measure which utilizes the designations of the Insurance Services Office ("ISO") and are reported with losses and loss settlement expense amounts net of reinsurance recoverables, unless specified otherwise. According to the ISO, a catastrophe loss is defined as a single unpredictable incident or series of closely related incidents that result in $25.0 million or more in U.S. industry-wide direct insured losses to property and that affect a significant number of insureds and insurers ("ISO catastrophe"). In addition to ISO catastrophes, we also include as catastrophes those events ("non-ISO catastrophes"), which may include U.S. or international losses, that we believe are, or will be, material to our operations, either in amount or in number of claims made. Management, at times, may determine for comparison purposes of our financial results that it is more meaningful to exclude extraordinary catastrophe losses and resulting litigation. The frequency and severity of catastrophic losses we experience in any year affect our results of operations and financial position. In analyzing the underwriting performance of our property and casualty insurance business, we evaluate performance both including and excluding catastrophe losses. Portions of our catastrophe losses may be recoverable under our catastrophe reinsurance agreements. We include a discussion of the impact of catastrophes because we believe it is meaningful for investors to understand the variability in our periodic earnings.
We consider our workers' compensation business to be a companion product; we rarely write stand-alone workers' compensation policies. Our workers' compensation insurance covers primarily small- to mid-size accounts. The net loss ratio improved 31.0 percentage points in 2019 compared to 2018. This improvement is attributable to the combination of three factors, decrease in reserves for newly reported claims which is due to fewer large claims in 2019, favorable prior year reserve development and a decrease in LAE reserves due to lower legal expenses.
The sale of our discontinued operations closed on March 30, 2018, and therefore income was only earned in the first quarter of 2018. For the year ended December 31, 2018, our discontinued operations had a loss before income taxes of $1.3 million, compared to income before income taxes of $10.6 million for the same period of 2017, respectively.
We reported a federal income tax expense on a consolidated basis of $2.1 million or 12.2 percent of pre-tax income in 2019. In 2018, federal income tax benefit on a consolidated basis of $3.3 million or 13.5 percent of pre-tax income and federal income tax benefit on a consolidated basis of $24.7 million or 94.1 percent of pre-tax income in 2017. In 2017 our effective tax rate was impacted by the Tax Act, which was enacted on December 22, 2017. The Tax Act significantly revised the U.S. corporate income tax laws including lowering the U.S. federal corporate tax rate from 35 percent to 21 percent effective January 1, 2018. Our effective federal tax rate varied from the statutory federal income tax expense rate in each year, due primarily to our portfolio of tax-exempt securities.
In 2019, 74.6 percent of our gross investment income from continuing operations originated from interest on fixed maturities, compared to 84.8 percent and 77.9 percent in 2018 and 2017, respectively.
In addition to these issues, other variables also contribute to a high degree of uncertainty in establishing reserves for construction defect claims. These variables include: whether coverage exists; when losses occur; the size of each loss; expectations for future interpretive rulings concerning contract provisions; and the extent to which the assertion of these claims will expand geographically. In recent years, we have implemented various underwriting measures that we anticipate will mitigate the amount of construction defect losses experienced. These initiatives include increased care regarding additional insured endorsements; stricter underwriting guidelines on the writing of residential contractors; and an increased utilization of loss control.
by $47.9 million and $5.6 million, respectively, while a 100 basis point increase in the rate would decrease the benefit obligation at December 31, 2019, by $37.2 million and $4.4 million, respectively.
For the post-retirement benefit plan, a 100 basis point increase in our estimated medical trend rate would increase the benefit expense for the year ended December 31, 2019, by $0.7 million, while a 100 basis point decrease in the rate would decrease benefit expense by $0.5 million, for the same period.
Depreciation expense totaled $10,482, $4,455 and $3,805 for 2019, 2018 and 2017, respectively.
We have several programs that provide reinsurance coverage. This reinsurance coverage limits the risk of loss that we retain by reinsuring direct risks in excess of our retention limits. The following table provides a summary of our primary reinsurance programs. Retention amounts reflect the accumulated retentions and co-participation of all layers within a program. For 2019, there was an all lines annual aggregate excess of loss program with variable retention of 6.66 percent of gross net earned premium with a minimum retention of $58.5 million and a maximum of $71.5 million. Our all lines aggregate recovery is also limited to $30.0 million. For 2018, there was an all lines annual aggregate excess of loss program with a variable retention of 6.78 percent of gross net earned premium with a minimum retention of $58.5 million and a maximum of $71.5 million. Our all lines aggregate recovery is also limited to a maximum of $30.0 million. For 2017, there was an all lines annual aggregate excess of loss program with a variable retention of 7.02 percent of gross net earned premium with a minimum retention of $58.5 million and a maximum of $71.5 million. Our all lines aggregate recovery is also limited to a maximum of $30.0 million.
The 2018 Life, accident and health business only includes results prior to the closing of the sale of United Life Insurance Company, which closed on March 30, 2018. Prior to the closing of the sale, United Fire & Casualty Company owned United Life Insurance Company, accordingly, the property and casualty statutory capital and surplus includes life, accident and health statutory capital and surplus, and therefore represents our total consolidated statutory capital and surplus.
Declining interest rates resulted in a decrease in the discount rates we use to value our respective plan's benefit obligations at December 31, 2019 compared to December 31, 2018.
We write both commercial and personal lines of property and casualty insurance. We focus on our commercial lines, which represented 93.3 percent of our property and casualty insurance premiums earned for 2019. Our personal lines represented 6.7 percent of our property and casualty insurance premiums earned for 2019.
UFG has agreed to provide services to Kuvare through a transition services agreement ("TSA"). The TSA ensures a seamless transfer of the business between UFG and Kuvare. The TSA includes, among other considerations, accounting management, human resources, legal and information technology services, from the closing date for up to 24 months. Since the close date, the Company has received $885 as part of the TSA.