What is the least common/most common type in each region?

Question

Also, this is individual typing, not the least common dual-type, as there are several that only have one. You'd add up all the Pokémon that have that typing.

Comments

Would this be the Pokemon available in the region before the postgame, or simply the generation of Pokemon?

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All pokemon available in the region(including postgame)

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"Over the seven generations, the water-type is the most common. This won't surprise Pokemon fans but what might is that poison is actually the most common in generation one. This is due to multiple dual-types however, as a lot of the grass-type Pokemon overlap with poison."
https://www.dexerto.com/pokemon/types-pokemon-all-regions-revealed-568467

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So just to be clear, if for, say, gen 3 (the Hoenn region), do you want the least common and most common type out of all the Hoenn Pokemon, or out of Pokemon introduced in all the generations leading up to the Hoenn region?

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About to set up a program to sort through each region, but I have a few questions:
1) I'm guessing pokemon with multiple forms that don't change types (Unown or Deoxys) should only be counted once, but what about Pokemon like Shaymin or Silvally that changes types? Should only the base form be counted?
2) Should megas be counted at all, and if yes, should they be counted as gen 6, when they were introduced, or as the same region as its base form?
3) I would guess that reginal variants would count as the region they were introduced (ie, Alolan Marowak is Gen 7, not Gen 1), right?
4) Should we only include new Pokemon added in each Gen, or should it be based off of the regional Pokedex for each region? If it's based off of the regional Pokedex, should I default to the most expansive version of that Pokedex, ie, HGSS reginal dex instead of GSC regional dex?

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This is another question I have, but its not that big of a deal as the other ones
Would Meltan/Melmetal count as being from Gen 1 or Gen 7? It was introduced during Gen 7, but was only first available in a Kanto game.

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1. Yes, the different forms with same type are counted once, both forms should be counted if there is more than one typing set for their forms.
2. No megas, unless a type change occurs because of the mega evolution. They should be counted as the region they are from(Mega Aerodactyl, Kalos, Mega Camerupt, Hoenn, etc.)
3. Yes
4. The regional pokedex, the most expansive one
5. Kanto

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Woops, number 5 was for JTP's question, and the first one you had JTP, all the pokemon catchable in Hoenn, as said in  answer number 4

Answer 1

KANTO (LGPE Dex):
Note: includes Megas only when a type change occurs
Most common: tie between Poison and Water with 33 species each
Lease common: Dark with Mega Gyarados as its sole species

JOHTO (HGSS Dex):
Megas and Fairy types are excluded because they did not exist in HGSS
Most common: Normal with 46 species
Least common: tie between Dragon and Ghost with 4 each

HOENN (ORAS Dex):
Most common: Water with 48 species
Least common: tie between Ghost and Ice with 8 each

Sinnoh (Pt Dex):
Note: excludes megas and Fairy types
Most common: Water with 35 species
Least common: Dragon with 7 species

Unova (B2W2 Dex):
Note: excludes megas and Fairy types
Most common: Water with 44 species
Least common: tie between Ghost and Dragon with 13 each

KALOS:
Note: includes megas only when a type change occurs
Most common: Water with 78 species
Least common: tie between Steel and Ghost with 24 each

ALOLA (USUM Dex):
Note: includes megas only when a type change occurs
Most common: Water with 81 species
Least common: Ice with 24 species

GALAR BASE (base Galar only):
Most common: Water with 62 species
Least common: Rock with 24 species

GALAR + DLC (all dexes combined, excluding duplicates):
Most common: Water with 96 species
Least common: Fire with 32 species

HISUI:
Most common: tie between Water and Flying with 36 each
Least common: Dragon with 10 species

Comments

I might be missing something here, but if you're using the most recent pokedex for each region, shouldn't the BDSP pokedex be used for Sinnoh? That would introduce Fairy types to that region and (probably - I haven't counted) make it the least common type.

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Hm, I was basing it off of the most expansive Pokedex, which puts Platinum 59 Pokemon above BDSP, but I didn't really think about Fairy types. I guess we'll see if MimikyuShadow wants me to use the BDSP Dex instead.

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For the LGPE Dex, shouldn't the Alolan variants be included (i.e. Alolan Muk and Alolan Persian)?

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How do you know this?

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Great answer, sorry it took kinda long, I didn't see it until really late last night, and I just got home like 10 min ago from school, this is great.

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Also, I'm fine with you using the Platinum Dex.

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Even if KRLW did, it would be the same, because I just counted and there are 8 Fairy Types in BDSP