Below is an instruction from Human. Write a response.
    ### Instruction:
    How many people are affected by color vision deficiency ?
    ### Response:
    Red-green color vision defects are the most common form of color vision deficiency. This condition affects males much more often than females. Among populations with Northern European ancestry, it occurs in about 1 in 12 males and 1 in 200 females. Red-green color vision defects have a lower incidence in almost all other populations studied.
    