evidence: Tax expenditures have a large effect on the federal budget. In fiscal year 2023, the value of the more than 200 tax expenditures in the individual and corporate income tax systems (including their effects on payroll taxes) is estimated to be $1.9 trillion, or 7.4 percent of GDP.27 That amount, which was calculated by CBO on the basis of estimates prepared by JCT, equals about 40 percent of all federal revenues in 2023 and exceeds projected outlays for all discretionary programs combined (see Figure 1-6). [...] Changes in fiscal policies also affect the economy in the longer term. In CBO’s projections, high and rising levels of federal borrowing reduce private investment activity in later years. In addition, the expiration of the temporary provisions of the 2017 tax act (P.L. 115-97)—including the expiration of most of the provisions affecting individual income taxes at the end of 2025 and the phaseout of bonus depreciation by the end of 2026—is projected to slow economic growth. [...] The Survey of Professional Forecasters