An amateur radio operator is someone who uses equipment at an amateur radio station to engage in two-way personal communications with other amateur operators on radio frequencies assigned to the amateur radio service. Amateur radio operators have been granted an amateur radio license by a governmental regulatory authority after passing an examination on applicable regulations, electronics, radio theory, and radio operation. As a component of their license, amateur radio operators are assigned a call sign that they use to identify themselves during communication. About three million amateur radio operators are currently active worldwide. Amateur radio operators are also known as radio amateurs or hams. The term "ham" as a nickname for amateur radio operators originated in a pejorative usage (like "ham actor") by operators in commercial and professional radio communities, and dates to wired telegraphy. The word was subsequently adopted by amateur radio operators. Demographics Few governments maintain detailed demographic statistics of their amateur radio operator populations, aside from recording the total number of licensed operators. The majority of amateur radio operators worldwide reside in the United States, Japan, and the nations of East Asia, North America, and Europe. The top five countries by percentage of the population are Japan, Slovenia, Taiwan, South Korea and Thailand. Only the governments of Yemen and North Korea currently prohibit their citizens from becoming amateur radio operators. In some countries, acquiring an amateur radio license is difficult because of the bureaucratic processes or fees that place access to a license out of reach for most citizens. Most nations permit foreign nationals to earn an amateur radio license, but very few amateur radio operators are licensed in multiple countries. Gender In the vast majority of countries, the population of amateur radio operators is predominantly male. In China, 12% of amateur radio operators are women, while approximately 15% of amateur radio operators in the United States are women. The Young Ladies Radio League is an international organization of female amateur radio operators. A male amateur radio operator can be referred to as an OM, an abbreviation used in Morse code telegraphy for "old man", regardless of the operator's age. A single female amateur radio operator can be referred to as a YL, from the abbreviation used for "young lady", regardless of the operator's age. A licensed married female is sometimes referred to as an XYL. Age Most countries do not have a minimum age requirement in