Including Duel-Types, there are:
Normal: There are currently 98 Normal-type pokemon.
Fire:There are currently 50 Fire-type pokemon.
Water: There are currently 110 Water-type pokemon.
Electric:There are currently 44 Electric-type pokemon.
Grass:There are currently 77 Grass-type pokemon.
Ice:There are currently 30 Ice-type pokemon.
Fighting:There are currently 41 Fighting-type pokemon.
Poison: There are currently 57 Poison-type pokemon.
Ground: There are currently 59 Ground-type pokemon.
Flying:There are currently 84 Flying-type pokemon.
Physic:There are currently 72 Psychic-type pokemon.
Bug:There are currently 65 Bug-type pokemon.
Rock:There are currently 47 Rock-type pokemon.
Ghost:There are currently 28 Ghost-type pokemon.
Dragon:There are currently 30 Dragon-type pokemon.
Dark:There are currently 39 Dark-type pokemon.
Steel:There are currently 38 Steel-type pokemon.
So, to sum up, the least amount is Ghost at a total of 28 known pokemon.
The reason this is probably because the ghost pokemon are often nigletted and mostly live in mountains.
Hope this answered your question!
