Age limit for HDI?
According to previous editions of Park (21st/e) the minimum and maximum established values for life expectancy atbirth was 25 years and 85 years, respectively.
 
However, Now the minimum established value is 20 years and maximum value is the highest observed value during time series, i.e. the country which has the highest value is taken as reference for maximum value. For example themaximum life expectancy is observed in Japan (83.4 in 2011). Thus 83.4 years is taken as
upper (maximum limit).

That means minimum value is established at 20 years and maximum value is established at 83.4 years.

Human development index (HDI)
o HDI is a composite index combining indicators representing three dimensions –
(i).  Longevity (life expectancy at birth)
(ii). Knowledge (Adult literacy rate and mean years ofschooling, i.e. Gross enrolement ratio)
(iii). Income (real GDP per capita in purchasing power parity in US dollars)
 
The HDI is an index used to rank countries by level of human development.
o According to HDI countries are divided -
(i).  Developed countries (High HDI → ≥0.8) →USA, Canada, Norway
(ii). Developing countries (medium HDI → 0.5-0.79)→India
(iii).  Underdeveloped countries (Low HDI → ≤0.5)→Seiera, Ethopia
 
Following information has been added in 22nd/e of Park
Components of human development index have changed. Now it includes expected years of schooling (insteadof adult literacy rate) and GNI per capita (instead of GDP per capita).
25 to 85 yrs
25 to 50 yrs
15 to 45 yrs
50 to 75 yrs