This obviously varies massively between denominations and even within denominations. I am trying to assess what percentage of Christendom takes early Genesis absolutely literally (six-day creation within the last 10,000 years, Noah's global flood, Adam and Eve as the first humans, etc.) as opposed to allegorically.
Here is some fairly recent data by those not friendly to creationism.
It looks like those who believe in creationism are 36%. While those who do not believe in evolution are 29%.
It is interesting to note that while falling, the percent change over the generations is not as steep as one might suspect.
There is also a graph where different denominations are polled about their belief in evolution. From Catholic = 58% to Evangelical = 23%
This might give some idea of the distribution.