The age group with the highest employment rate varies across countries and can change over time due to various factors such as economic conditions, labor market policies, and demographics. However, I can provide you with some general trends and examples based on available data.

 1. Prime Working Age Group (25-54 years):
 The prime working age group typically has a higher employment rate compared to other age groups. These individuals are often considered to be in their peak working years, with more experience and skills, making them more employable. For instance, in the United States, the employment-population ratio for the prime working age group was around 77% as of September 2021, according to the Bureau of Labor Statistics (BLS) data. This group includes individuals who have completed their education, gained work experience, and are actively participating in the labor force.

 2. Older Workers (55 years and above):
 In recent years, there has been a notable increase in employment rates among older workers. Factors such as increasing life expectancy, changes in retirement patterns, and financial needs have led many individuals to continue working beyond traditional retirement ages. For example, countries like Japan and South Korea have witnessed a rise in employment rates among older workers due to their aging populations and policy changes to encourage longer workforce participation.

 3. Youth (15-24 years):
 The youth employment rate tends to be lower compared to other age groups due to factors such as lack of work experience, limited skills, and competition for entry-level jobs. However, this can vary significantly across countries. For instance, in countries with robust economies and well-established education-to-employment systems, youth employment rates might be higher. On the other hand, in countries facing economic challenges or high youth unemployment rates, such as Spain or Greece, the youth employment rate might be lower.

 It is important to note that the employment rate can be influenced by various factors, including the overall economic situation, educational attainment, gender disparities, and government policies. Therefore, it is crucial to refer to specific data and sources for accurate and up-to-date information on employment rates by age group in a particular country or region.