The correct option is 2 and 3 only.
Explanation
The Human Development Index (HDI), published by the United Nations Development Programme (UNDP), measures average achievement in three key dimensions of human development: a long and healthy life, access to knowledge, and a decent standard of living. The dimension of 'Access to Knowledge' is assessed through specific educational indicators.
Statement-wise Analysis:
- Statement 1 is Incorrect. Vocational training rate is not a component of the Human Development Index. While vocational training is crucial for skill development and employability, it is not used as a standard global metric for the HDI calculation.
- Statement 2 is Correct. The Gross Enrolment Ratio (GER) represents the number of students enrolled in a given level of education, regardless of age, expressed as a percentage of the official school-age population. While the current HDI methodology (post-2010) primarily uses "Expected Years of Schooling," GER was a fundamental indicator in the original HDI methodology (combined with adult literacy). In the context of this question, it is recognized as a metric representing access to education.
- Statement 3 is Correct. Mean years of schooling is a primary indicator in the current HDI methodology. It represents the average number of years of education received by people ages 25 and older, converted from education attainment levels using official durations of each level.
Key Takeaway:
The current Human Development Index (HDI) measures the 'Knowledge' dimension using Mean Years of Schooling (for adults) and Expected Years of Schooling (for children). Older methodologies utilized Adult Literacy Rate and Gross Enrolment Ratio.