(2) Effective December 31, 2018, as a result of the acquisition of Express Scripts (see Note 3 to the Consolidated Financial Statements), the Company adopted Article 5 of Regulation S-X issued by the Securities and Exchange Commission. As a result, realized investment results are no longer included in revenues. Prior year revenues have been adjusted to conform to the new presentation.
Cigna Corporation, together with its subsidiaries (either individually or collectively referred to as "Cigna," the "Company," "we," "our" or "us") is a global health service organization dedicated to a mission of helping those we serve improve their health, well-being and peace of mind. Our evolved strategy in support of our mission is Go Deeper, Go Local, Go Beyond using a differentiated set of medical, pharmacy, dental, disability, life and accident insurance and related products and services offered by our subsidiaries. For further information on our business and strategy, see Item 1, "Business" in this Form 10-K.
Cash flows from operating activities decreased in 2018 compared with 2017 primarily driven by the timing of settlement of pharmacy payables, partially offset by higher net income.
Net investment purchases increased in 2018 compared with 2017, largely due to reinvesting our cash flows into fixed income investments. The decrease in net investment purchases in 2017 compared with 2016 primarily reflects higher cash used for share repurchases in 2017.
• is covered under a medical insurance policy, managed care arrangement or service agreement issued by us;
The acquisition cost ratio increased due to higher amortization primarily in Korea and Taiwan.
South Korea is the single largest geographic market for our International Markets segment. South Korea generated 40% of the segment's revenues and 68% of the segment's pre-tax adjusted income from operations in 2018. In 2018, our International Markets segment operations in South Korea represented 5% of our consolidated revenues and 11% of consolidated pre-tax adjusted income from operations.
• selling, general and administrative expense as a percentage of revenues excluding net investment income (expense ratio).
Adjusted revenues decreased slightly, due to the continued run-off of international business and lower life premiums, mostly offset by moderate growth in the group disability business and higher investment income.
Corporate reflects amounts not allocated to operating segments, including net interest expense (defined as interest on corporate debt less net investment income on investments not supporting segment and other operations), certain litigation matters, compensation cost for stock options, expense associated with our frozen pension plans, charitable contributions, severance, certain overhead and project costs and intersegment eliminations for products and services sold between segments.
The Company's management is responsible for these consolidated financial statements, for maintaining effective internal control over financial reporting, and for its assessment of the effectiveness of internal control over financial reporting, included in the accompanying Management's Annual Report on Internal Control over Financial Reporting. Our responsibility is to express opinions on the Company's consolidated financial statements and on the Company's internal control over financial reporting based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) ("PCAOB") and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.
Rebates from pharmaceutical manufacturers resulting from ASO client utilization at retail pharmacies, net of amounts payable to ASO clients, are compensation for pharmacy services and recorded in fees and other revenues. Rebates generally represent a per-script amount from the manufacturer and are determined based on scripts filled during the reporting period.
• Old Cigna completed a cash tender offer to purchase $1.0 billion of aggregate principal amount of certain of its outstanding debt securities in the third quarter of 2017 and recorded a pre-tax loss of $321 million ($209 million after-tax), primarily for premiums paid. Old Cigna repaid $131 million and $250 million of long-term notes that matured during the first quarter of 2018 and 2017 respectively.
Accounting policy. Commercial mortgage loans are carried at unpaid principal balances or, if impaired, the lower of unpaid principal or fair value of the underlying real estate. See the "Impaired commercial mortgage loans" section below for the Company's accounting policy for impaired commercial mortgage loans. Commercial mortgage loans are classified as either current or long-term investments based on their contractual maturities.
Assets in Level 1 include actively-traded U.S. government bonds and exchange-listed equity securities. A relatively small portion of the Company's investment assets are classified in this category given the narrow definition of Level 1 and the Company's investment asset strategy to maximize investment returns.
Accounting policy. Separate account assets and liabilities are contractholder funds maintained in accounts with specific investment objectives. The assets of these accounts are legally segregated and are not subject to claims that arise out of any of the Company's other businesses. These separate account assets are carried at fair value with equal amounts recorded for related separate account liabilities. The investment income and fair value gains and losses of these accounts generally accrue directly to the contractholders and, together with their deposits and withdrawals, are excluded from the Company's Consolidated Statements of Income and Cash Flows. Fees and charges earned for
Other postretirement benefit plans. The Company's postretirement medical plan was frozen in 2013. The Company also offers certain postretirement life insurance benefits through various plans.
Management determined the present value of the projected benefit obligation and the accumulated other postretirement benefit obligation and related benefit costs based on the following weighted average assumptions as of and for the years ended December 31: