Effort values

Effort values, often abbreviated as EVs, are an important part of Pokémon training to consider. While raising a Pokémon's level is a very important part of its training, making sure that a Pokémon gains effort points in the correct stats is just as important to making the Pokémon the best it can be. For a list of the effort points that Pokémon give away on their defeat, see List of Pokémon by effort value yield.

Overview

Generation I

In Generation I, the basic EV system was introduced. Each Pokémon would give out either 1, 2, or 3 effort points, depending on its species, in a particular stat (Attack, Defense, Speed, Special, or HP). With these effort points, a Pokémon would get stronger in a specific stat by battling the same kind of Pokémon over and over. For example, battling Jolteon after Jolteon would cause a Pokémon to eventually have a higher Speed.

At level 100, a Pokémon's stats will be one point higher in a specific stat for every four effort points gained in that stat compared to an untrained counterpart. Though leveling up stops at 100, addition of effort values can continue indefinitely, until the Pokémon reaches the maximum possible value for their stats using the box trick, where a Pokémon's stats are recalculated to reflect the amount of effort points it has gained when it is deposited in a PC.

Generation II

The basic structure did not change much in Generation II, excepting the fact that now, instead of having five stats, there were six. Both Special Attack and Special Defense were calculated using the effort points for Special, causing both to rise by the same amount for each and every Pokémon. Like in Generation I, the box trick could be performed.

The PokéRus virus, a rare status condition, was also introduced. It would double the amount of effort points gained in battle.

Generation III

In Generation III, the effort value structure, like many other things, was overhauled completely. A Pokémon now could not have an effectively infinite amount of training, but was limited to 510 effort points total, with 255 effort points being the maximum for an individual stat. This mean that two stats could be maxed out (with 252 being the highest number evenly divisible by four), while another stat could get one more point. The vitamins of the previous two generations would also not merely add stat points, but instead added 10 effort points to a specific stat, and could not be used if the specific stat was at or above 100 effort points, or the total effort points amounted to 510 or more. Likewise, the Special Attack and Special Defense stats were finally split, and Zinc was introduced so as to give the Special Defense stat a vitamin enhancement.

A held item, the Macho Brace, was also introduced; it would double the amount of effort points gained in battle, providing for faster training. Utilized with the PokéRus, which makes a return, it provides four times the amount of effort points per Pokémon.

Also, in Pokémon Emerald, certain Berries that were previously only used to make Pokéblocks were now able to decrease effort points gained by 10, while increasing the happiness of the Pokémon they were used on.

Generation IV

While not much changed from Generation III, due mostly to the data structure remaining much the same, a series of items were introduced that would automatically add four effort points per Pokémon battled in a specific stat.

Stat	Item
HP	Power Weight
Attack	Power Bracer
Defense	Power Belt
Special Attack	Power Lens
Special Defense	Power Band
Speed	Power Anklet

They would, however, also add whatever the Pokémon defeated would naturally add; for example, a Pokémon defeating a Bidoof while holding the Power Lens would get 4 Special Attack effort points, as well as the 1 HP effort point Bidoof naturally rewards, while defeating a Bidoof while holding the Power Weight would yield 5 HP effort points.