We have typically funded our day-to-day liquidity by issuing commercial paper. In the third and fourth quarters of 2020, we reduced our commercial paper issuances as compared to the prior year period primarily as a result of the issuance of the 4.20% Notes in April 2020. In 2019, we issued short-term debt in a private placement to reduce our commercial paper issuances. This short-term debt was redeemed in the third quarter of 2019. Additional liquidity sources include our Credit Facility, 364 Day Credit Facility or the uncommitted credit lines. At December 31, 2020, there were no outstanding commercial paper issuances or borrowings under the Credit Facility, the 364 Day Credit Facility or the uncommitted credit lines. Commercial paper activity was (dollars in millions): Year Ended December 31, 2020 2019 2018 Average amount outstanding during the year $ 50.1  $ 272.3  $ 411.7  Maximum amount outstanding during the year $ 401.2  $ 825.0  $ 1,218.7  Average days outstanding 4.6  4.0  5.7  Weighted average interest rate 1.52 % 2.40 % 2.19 % We expect to continue issuing commercial paper to fund our day-to-day liquidity. However, disruptions in the credit markets may lead to periods of illiquidity in the commercial paper market and higher credit spreads. To mitigate any disruption in the credit markets and to fund our liquidity, we may borrow under the Credit Facility, 364 Day Credit Facility or the uncommitted credit lines or access the capital markets if favorable conditions exist. We will continue to monitor closely our liquidity and conditions in the credit markets. We cannot predict with any certainty the impact on us of any disruptions in the credit markets. In such circumstances, we may need to obtain additional financing to fund our day-to-day working capital requirements. Such additional financing may not be available on favorable terms, or at all. We manage our exposure to foreign exchange and interest rate risk through various strategies, including the use of derivative financial instruments. We use forward foreign exchange contracts as economic hedges to manage the cash flow volatility arising from foreign exchange rate fluctuations. We may use interest rate swaps to manage our interest expense and structure our long-term debt portfolio to achieve a mix of fixed rate and floating rate debt. We do not use derivatives for trading or speculative purposes. Using derivatives exposes us to the risk that counterparties to the derivative contracts will fail to meet their contractual obligations. We manage that risk through careful selection and ongoing evaluation of the counterparty financial institutions based on specific minimum credit standards and other factors. We evaluate the effects of changes in foreign currency exchange rates, interest rates and other relevant market risks on our derivatives. We periodically determine the potential loss from market risk on our derivatives by performing a value-at-risk, or VaR, analysis. VaR is a statistical model that uses historical currency exchange rate data to measure the potential impact on future earnings of our derivative financial instruments assuming normal market conditions. The VaR model is not intended to represent actual losses but is used as a risk estimation and management tool. Based on the results of the model, we estimate with 95% confidence a maximum one-day change in the net fair value of our derivative financial instruments at December 31, 2020 was not significant. In 2020, our international operations represented approximately 45% of our revenue. Changes in the value of foreign currencies against the U.S. Dollar affect our results of operations and financial position. For the most part, because the revenue and expenses of our foreign operations are denominated in the same local currency, the economic impact on operating margin is minimized. The effects of foreign currency exchange transactions on our results of operations are discussed in Note 2 to the consolidated financial statements. We operate in all major international markets including the Euro Zone, the U.K., Australia, Brazil, Canada, China and Japan. Our agencies transact business in more than 50 different currencies. As an integral part of our global treasury operations, we centralize our cash and use notional multicurrency pools to manage the foreign currency exchange risk that arises from imbalances between subsidiaries and their respective treasury centers. In addition, there are circumstances where revenue and expense transactions are not denominated in the same currency. In these instances, amounts are either promptly settled or hedged with forward foreign exchange contracts. To manage this risk, at December 31, 2020 and 2019, we had outstanding forward foreign exchange contracts with an aggregate notional amount of $169.6 million and $284.2 million, respectively. At December 31, 2020 and 2019, the net fair value of the forward foreign contracts was not material (see Note 20 to the consolidated financial statements). Foreign currency derivatives are designated as economic hedges; therefore, any gain or loss in fair value incurred on those instruments is generally offset by decreases or increases in the fair value of the underlying exposure. By using these financial instruments, we reduce financial risk of adverse foreign exchange changes by foregoing any gain which might occur if the markets move favorably. The terms of our forward foreign exchange contracts are generally less than 90 days. Foreign Currency Exchange Risk Item 7A. Quantitative and Qualitative Disclosures About Market Risk 28