Pokémon Gold Version, Silver Version, and Crystal Version - Stat Experience
Stat experience (Stat Exp) refers to a set of values that indicate a Pokémon’s training. There are five stat experience values: HP, Attack, Defense, Speed, Special. Whenever an enemy Pokémon is defeated, the participants in defeating that Pokémon earn stat experience, similar to normal experience . (Each participant earns stat experience even if its level is 100.)
After a Pokémon is defeated, for each stat, an amount equal to the corresponding Race Value of the defeated Pokémon is distributed among all participants in the battle against it (see the experience page).
A Pokémon starts with zero stat experience points for all stats. A Pokémon can have up to 65,535 stat experience points per stat, after which it can’t earn any more.
A Pokémon’s stats are calculated upon creation. A Pokémon’s stats are recalculated when it gains a level, when it’s placed in a Box or in the Daycare, when it evolves, or when a Rare Candy, HP Up, Protein, Iron, Carbos, or Calcium is given to it and takes effect.
Using a Rare Candy provides no stat experience: it simply raises a Pokémon’s level.
Stat-Boosting Items
The items HP Up, Protein, Iron, Carbos, and Calcium increase the stat experience for HP, Attack, Defense, Speed, and Special, respectively, by 2,560 (even if the stat experience would increase to 25,600 or more), but each such item won’t have any effect when a Pokémon’s stat experience for the respective stat is 25,600 or greater . These items also update all of a Pokémon’s stats after increasing stat experience.
The Box Trick
When a Pokémon is placed in a PC storage box, the game stores, among other things, its experience (to calculate its level), its DVs, and the amount of stat experience it currently has for each stat. When the Pokémon is removed from the storage system, its stats are recalculated based on its stat experience, without actually gaining a level. This effect is called the "box trick."
Special Stat Experience
A Pokémon’s Special Attack and Special Defense are calculated using its Special DV and Special stat experience, and a battle’s participants gain Special stat experience according to the base Special Attack of the foe when it is defeated.