Item 7A. QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK

Foreign Currency Exchange Rate Risk

Certain of our operations are conducted in foreign currencies. Consequently, a portion of our revenues and expenses may be affected by fluctuations in foreign currency exchange rates. We have not historically hedged our translation risk on foreign currency exposure, but we may do so in the future. For the years ended December 31, 2018 and 2017 and the 2016 fiscal transition period, currency rate fluctuations calculated by converting revenues and expenses for the current year in local currency using the prior-year period rates had an immaterial effect on our revenues and operating income. For the year ended May 31, 2016, currency rate fluctuations reduced our revenues by $117.0 million and our operating income by $43.6 million as compared to the prior-year period, calculated by converting revenues and expenses for the year ended May 31, 2016 in local currency using prior-year period rates.

Generally, the functional currency of our various subsidiaries is their local currency. We are exposed to currency fluctuations on transactions that are not denominated in the functional currency. Gains and losses on such transactions are included in determining net income for the period. We seek to mitigate our foreign currency risk through timely settlement of transactions and cash flow matching, when possible. For the years ended December 31, 2018 and 2017, the 2016 fiscal transition period and the year ended May 31, 2016, our transaction gains and losses were insignificant.

Additionally, we are affected by currency fluctuations in our funds settlement process on merchant payment, chargeback and card network settlement transactions that are not denominated in the currency of the underlying credit or debit card transaction. Gains and losses on these transactions are included in revenues for the period.

We are also affected by fluctuations in exchange rates on our investments in foreign operations. Relative to our net investment in foreign operations, the assets and liabilities of subsidiaries whose functional currency is a foreign currency are translated at the period-end rate of exchange. The resulting translation adjustment is recorded as a component of other comprehensive income and is included in shareholders' equity. Transaction gains and losses on intercompany balances of a long-term investment nature are also recorded as a component of other comprehensive income.

Interest Rate Risk

We are exposed to market risk related to changes in interest rates on our long-term debt and cash investments. We invest our excess cash in securities that we believe are highly liquid and marketable in the short term. These investments earn a floating rate of interest and are not held for trading or other speculative purposes.

We have a Credit Facility for general corporate purposes, as well as various lines of credit that we use to fund settlement in certain of our markets. Interest rates on these debt instruments and settlement lines of credit are based on market rates and fluctuate accordingly. As of December 31, 2018, the amount outstanding under these variable-rate debt arrangements and settlement lines of credit was $5.9 billion.

The interest earned on our invested cash and the interest paid on our debt are based on variable interest rates; therefore, the exposure of our net income to a change in interest rates is partially mitigated as an increase in rates would increase both interest income and interest expense, and a reduction in rates would decrease both interest income and interest expense. Under our current policies, we may selectively use derivative instruments, such as interest rate swaps or forward rate agreements, to manage all or a portion of our exposure to interest rate changes. We have interest rate swaps that reduce a portion of our exposure to market interest rate risk on our LIBOR-based debt as discussed in "Note 8—Long-Term Debt and Lines of Credit" in the notes to our accompanying consolidated financial statements.

Based on balances outstanding under variable-rate debt agreements and invested cash balances at December 31, 2018, a hypothetical increase of 50 basis points in applicable interest rates as of December 31, 2018 would increase our annual interest expense by approximately $17.5 million and increase our annual interest income by approximately $3.3 million.