AMSTERDAM (AP) — Twenty years ago, the mayor of Amsterdam married four couples in City Hall as the Netherlands became the first country with legalized same-sex marriages. Today, same-sex marriage is legal in 28 countries worldwide, including most of Western Europe. Yet its spread has been uneven. The self-governing island of Taiwan is the only place in Asia to take the step; South Africa is the only African country to do so. Added together, the countries with same-sex marriage are home to about 1.2 billion people, roughly 15% of the world’s population. They include 16 countries in Western Europe, the United States, Canada, Costa Rica, five South American countries, Australia and New Zealand.