A part-time contract is a form of employment that carries fewer hours per week than a full-time job. Workers are considered to be part-time if they commonly work fewer than 30 or 35 hours per week. According to the International Labour Organization, the number of part-time workers has increased from one-fourth to a half in the past 20 years in most developed countries, excluding the United States. There are many reasons for working part-time, including the desire to do so, having one's hours cut back by an employer and being unable to find a full-time job. The International Labour Organisation Convention 175 requires that part-time workers be treated no less favourably than full-time workers. In some cases the nature of the work itself may require that the employees be classified part as part-time workers. For example, some amusement parks are closed during winter months and keep only a skeleton crew on hand for maintenance and office work. As a result of this cutback in staffing during the off season, employees who operate rides, run gaming stands, or staff concession stands may be classified as part-time workers owing to the months long down time during which they may be technically employed but unable to work. "Part-time" can also be used in reference to a student (usually in higher education) who takes only a few courses, rather than a full load of coursework each semester.