I belief the Fields Medal is not only given to people below 40 b/c there are no older people deserving; I belief it is given to younger people b/c they can most benefit from getting such recognition.
The Fields Medal is awarded every four years on the occasion of the International Congress of Mathematicians to recognize outstanding mathematical achievement for existing work and for the promise of future achievement.
A candidate's 40th birthday must not occur before January 1st of the year of the Congress at which the Fields Medals are awarded.
A candidate's 40th birthday must not occur before January 1st of the year of the Congress at which the Fields Medals are awarded.