na-adjective
progressive; graduated
Used especially for tax rates, fees, or systems that increase in steps according to a scale. Often appears in economic or policy contexts.
累進的な税率が導入された。
A progressive tax rate was introduced.
この制度は累進的な料金体
This system adopts a graduated fee structure.
比例 means 'proportional' and is used for flat-rate systems, contrasting with 累進的 which implies increasing rates.
Formed from 累進 (progressive increase) + the adjectival suffix 的. The exact historical derivation is uncertain, but the term is a modern compound used in economic and policy language.