within the President's Budget (OMB) provide a wide range of data on federal government finances. Many of the data series begin in 1940 and include estimates of the President's Budget for 2018–2023. Additionally, Table 1.1 provides data on receipts, outlays, and surpluses or deficits for 1901–1939 and for earlier multi-year periods. This document is composed of 17 sections, each of which has one or more tables. Each section covers a common theme. Section 1, for example, provides an overview of the budget and off-budget totals; Section 2 provides tables on receipts by source; and Section 3 shows outlays by function. When a section contains several tables, the general rule is to start with tables showing the broadest overview data and then work down to more detailed tables. The purpose of these tables is to present a broad range of historical budgetary data in one convenient reference source and to provide relevant comparisons likely to be most useful. The most common comparisons are in terms of proportions (e.g., each major receipt category as a percentage of total receipts and of the gross domestic product). Federal budget projections The Congressional Budget Office (CBO) projects budget data such as revenues, expenses, deficits, and debt as part of its "Long-term Budget Outlook" which is released annually. The 2018 Outlook included projections for debt through 2048 and beyond. CBO outlined several scenarios that result in a range of outcomes. The "Extended Baseline" scenario and "Extended Alternative Fiscal" scenario both result in a much higher level of debt relative to the size of the economy (GDP) as the country ages and healthcare costs rise faster than the rate of economic growth. CBO also identified scenarios involving significant austerity measures, which maintain or reduce the debt relative to GDP over time. CBO estimated the size of changes that would be needed to achieve a chosen goal for federal debt. For example, if lawmakers wanted to reduce the amount of debt in 2048 to 41 percent of GDP (its average over the past 50 years), they might cut non-interest spending, increase revenues, or take a combination of both approaches to make changes that equaled 3.0 percent of GDP each year starting in 2019. (In dollar terms, that amount would total about $630 billion in 2019.) If, instead, policymakers wanted debt in 2048 to equal its current share of GDP (78 percent), the necessary changes would be smaller (although