Income splitting is a tax policy of fictionally attributing earned and passive income of one spouse to the other spouse for the purposes of assessing personal income tax (i.e. "splitting" away the income of the greater earner, reducing his/her income for tax measurement purposes), thus reducing tax rates paid by the spouse who earns more and increasing rates paid by a spouse who earns less (or nothing). Global incidence and ramifications for sovereign debt and fertility rates Most Western countries have abolished mandatory fictional income splitting, while in several countries fictional income splitting is optional (if the couple chooses it). A 2009 study of 26 European countries found that: "In France, Liechtenstein, Luxembourg and Portugal, couples are jointly assessed. Ireland and Germany operate joint taxation, respectively, with an option for individual taxation and the right to be individually taxed when this is more advantageous; conversely individual taxation is the default option in Spain and Poland, but the option of joint assessment is offered. Elements of jointness remain in some income tax codes for which the individual is the unit of taxation – the Belgian, Estonian, Greek, Icelandic and Norwegian codes – some of which are minor while others matter. The remaining countries enforce individual income taxation without exceptions". In 2015, Portugal abolished the mandatory joint taxation of a family, establishing separate taxation for married (or de facto unions) taxpayers as the norm, with an option being available for joint taxation. The International Monetary Fund has called for the countries to abandon the practice of taxing family income instead of individual income, along with other tax practices, such as the method of assessing payroll tax in the United States, which assesses extra taxes, higher tax rates, and reduced benefits to families that have two earners, and provides funded and unfunded subsidies to patriarchal families, which are related to sovereign debt problems in these countries. In the United States, the spouse to whom the income is fictionally attributed does not pay payroll tax on that "split" earned income, while the benefit of that spouse's lower rate does accrue to the greater earner. The "split" is thus ignored in that context while it is applied in the income tax context. Even though the fictionally earning spouse does not pay payroll tax, the couple draws two sets of Social Security and Medicare benefits. Declining fertility rates in countries that subsidize patriarchal/maternalist marriage and rebounding