The single most significant aspect of the New Zealand parliamentary system is that it is Westminster-based. The power of the New Zealand Parliament is the starker because, since 1951, it has been vested solely in the popularly elected House of Representatives. From Westminster there came also the single-member plurality voting system — the first-past-the-post voting system — and political tradition of a two-party oligopoly, the voting system reinforcing the tradition. New Zealand's voting system, dubbed Mixed Member Proportional (MMP), is an adaptation of the post-war German voting system. The MMP system, as intended and expected by its architects and proponents, has ended the two-party oligopoly, producing a multi-party Parliament in which no one party has a majority. Parliament's powers are restricted both by traditional powers of the monarchy which the Crown and government need not share with Parliament, and by the executive control over finance.