Effort value

Effort values, abbreviated EVs, are hidden statistics that increase your Pokémon's battle stats, in proportion to your Pokémon's level. The Pokémon in your team accumulate these points as they defeat other Pokémon in battle. Because of this, your Pokémon become stronger than wild Pokémon at the same level, simulating the support and training they get from you.
==Over the Generations==
These stats have always existed in some form in all core Pokémon games, but have taken a couple turns through the generations.
===Gen I and II===
In these games, your Pokémon have a "stat experience" number associated with each of their 5 stats (HP, Attack, Defense, Special, and Speed). When they defeat a Pokémon, the defeated Pokémon's base stats are added onto that number, each one maxing out at 65535. You can calculate this number by getting the stat difference between a trained and untrained Pokémon at the same level (100 being the simplest) and putting it into this formula:
\gamma = 16\sigma^2
Where σ is the difference at level 100 and γ is the Pokémon's current experience in a stat. A bit of algebra gets you the reverse if you know the experience and want to know how much extra it would give to the stat at level 100:
\sigma = \frac{\sqrt \gamma }{4}
For example, two level 100 Chanseys have 20 difference in their HP and one is untrained:
\gamma = 16(20)^2 = 6400 HP experience
===Gen III===
The system was entirely overhauled in the third generation (Ruby, Sapphire and Emerald). This was the generation when EVs were most widely noticed and recognized, and any mention of EVs almost always refers to this overhaul. Every generation since has used this method.
Every unique species of Pokémon has assigned to it a number of 1, 2, or 3 distributed to one or more stats. Pokémon earn that number for that stat when they defeat that Pokémon. For example, Chansey will give 2 HP EVs, Meganium will give 1 Defense EV and 2 Special Defense EVs, and Sneasel will give 1 Speed EV.
Your Pokémon can have a maximum of 255 EVs in any one stat and a maximum of 510 between all stats together. For any Pokémon at level 100, every 4 EVs it has increases the stats you can see by 1. Lower levels scale down linearly from there, so you can get a simple estimate of a Pokémon's EV total and distribution by comparing with an untrained Pokémon of the same species at any of the same levels.
This means after accumulating 510 EVs, the game will stop tallying them and EV training becomes useless for that Pokémon. After you gain all of your EVs, the total increase in stats for your Pokémon will be +127 at level 100. After your Pokémon has gained 255 EVs on a stat (such as Attack), the game will stop tallying EVs for that stat. This means that the said stat will cap off with +63 at level 100. This doesn't mean that it has to stop gaining EVs, it just means that once it hits that mark, it'll have to get EVs in another stat, such as Defense or Special Attack.
This also means you cannot gain +63 in every stat like you could in Gen I and II, better reflecting each of your Pokémon's overall history in battle. You can also select specific Pokémon to battle, so the full 510 EVs are distributed exactly as you wish. This is tedious, but important for competitive strategy.
===Gen VI===
Pokémon X and Pokémon Y introduced Super Training, an alternative way to gain EVs. This was the first time EVs were put on display for the player. It officially dubbed them "base stats", although by that time EVs had already been thoroughly examined and discussed by the community of players.
==Training Methods==
===Making the Process Easier===
EV training can become a very tedious process. Fortunately, there are items and effects that can make this whole process go by much more quickly.
*Macho Brace. This doubles the amount of EVs gained in a battle. For example, if you beat a Machoke, instead of getting 2 ATK Evs, you would get 4 ATK EVs.
*"Power" Items (Generation IV and later). These items will only work for one stat and will reduce the Pokémon's speed while held. They increase the described stat by four. These are Power Weight (HP), Power Bracer (ATK), Power Belt (DEF), Power Lens (SPATK), Power Band (SPDEF) and Power Anklet (SPD). If your Pokémon was holding a Power Bracer (ATK) and it beat a Machoke, instead of 2 ATK EVs, you would get 2 + 4 = 6 ATK EVs; If your Pokémon was holding a Power Belt and it beat a Machoke, besides getting the 2 EVs on attack, you would also get 4 EVs on Defense.
*Pokérus. This is a very rare beneficial virus (made less and less rare in newer versions) that can be obtained in battles against wild Pokémon. It has the same effect as the Macho Brace, but will wear off if the infected Pokémon is in your party when the DS internal clock reached midnight. However, the virus can be kept indefinitely if the Pokémon is kept in the Box. Can be passed along party Pokémon by battling; it will pass to any Pokémon situated next to the infected Pokémon after a battle. NOTE: It might not pass after any battle, as it may pass, it is random. How it works: Imagine your Pokémon is holding a Power Bracer and defeats a wild Machoke; it would get (2 + 4)*2 = 12 ATK EVs. Another example: Your Pokémon is holding a Power Belt and it defeats a Wild Machoke; you will get 2*2 = 4 ATK Evs and 4 DEF EVs.
*HP UP, Protein, Iron, Calcium, Zinc and Carbos. These add 10 EVs to their respective stat until a cap of 100 EVs. Very practical as they cost 1 BP.
*Wings, introduced in the 5th generation (White, Black, White 2, Black 2), give you 1 EV per use. They aren't very effective alone, but in large amounts can be very helpful. They are perfect for you if you don't want to battle one specific Pokémon when their encounter rate is very low. A Resist Wing will give you 1 EV for Defense, whereas a Genius Wing will give 1 EV for Special Attack.
===Lowering EVs===
Because you have to work under 510 EVs, you may find it useful to be able to reduce specific EVs to tune them to your liking. Emerald gave a new function to six Berries: raise friendship and reduce EVs by 10. It works in all games since.
*A Pomeg Berry reduces HP EVs.
*A Kelpsy Berry reduces Attack EVs.
*A Qualot Berry reduces Defense EVs.
*A Hondew Berry reduces Sp. Atk EVs.
*A Grepa Berry reduces Sp. Def EVs.
*A Tamato Berry reduces Speed EVs.
Super Training has a Reset Bag that wipes a Pokémon's EVs completely clean. This is the quickest and easiest way to reduce EVs, but only available in Gen VI.
Category:Stats
Category:Game Mechanics