The ILO (International labor Organisation) standard for the lower age limit is 15 years. However, it may vary slightly from country to country. Some countries have an upper limit, such as 65 or 70 years, although this requirement is seldom imposed.
Working-age population is usually broken down by age and sex:
Youth, aged 15 to 24 years.
Adult, aged 25 and over.
Male and female working populations.
Source: ILO (International Labour Organisation): Key Indicators of the Labour Market, 9th edition.