Dynamic Scoring: An Introduction to the Issues
介绍美国国会预算办公室和联合税收委员会在收入预测中使用的动态评分方法，解释基线预测与评分之间的相互依赖关系，并讨论宏观反馈效应缺失导致的不一致性。
Working together, CBO and JCT provide two types of revenue and expenditure projections for Congress: (i) forecasts of expenditures and revenues based on assumptions about what “current” policy is, and (ii) forecasts of the changes in expenditures and revenues that would result from proposed legislation. The first type of forecast is known as a baseline. The second type is called scoring. The two types of forecasts are interdependent. Projected effects of legislation depend on the starting point, so the baseline affects scoring. Updates of the baseline reflect the estimated impact of legislation, so scoring affects the baseline. On the revenue side, where dynamic scoring has received the greatest attention, the baseline forecasts are provided to Congress by CBO, while scoring is done by the JCT. In a sense, the debate over dynamic scoring may be traced to an inconsistency in the way that legislative changes are handled by the two agencies. Macroeconomic feedback effects are ultimately incorporated in CBO’s baseline but are not attributed by JCT to any source when the proposals are scored. This inconsistency is most easily understood in terms of relative informational requirements. One can update a baseline to account for macroeconomic changes without attributing these changes to particular legislation. Indeed, the models used to construct baselines are not specified at the level of detail that would be necessary to do so. Under standard scoring procedures, JCT scores proposed legislation taking the macroeconomic forecast underlying the CBO baseline (including nominal GDP and other aggregates) as given. It is misleading to refer to these revenue estimates as “static,” because they do take certain behavioral effects into account. For example, when JCT scores a change in the capitalgains tax rate, it includes the revenue offset associated with changes in capital-gains realizations. But missing is any further impact on revenues or expenditures that might result from induced changes in output, interest rates, or other elements of the macroeconomic forecast. Thus, current scoring estimates incorporate “micro” dynamic effects, but not “macro” ones.