3. Using quarterly data since 1960, graph the following four series, expressing each as a percent of GDP: exports of goods (sometimes called merchandise), exports of services, imports of goods (sometimes called merchandise), and imports of services. What trends do you notice in U.S. exports and imports of goods and services? When computing the percentage of GDP, you should note that quarterly data on exports and imports often are not expressed at annual rates, but the data on GDP are expressed at annual rates; if this is the case with your data, multiply your data on imports and exports by 4 to get the appropriate ratio relative to GDP.