Between 20-25% of the population report symptoms of IBS at some point in their lives. Women seem to present more commonly with IBS symptoms. Many people have symptoms but may not go to their doctor, or may not fit the criteria for diagnosis by a doctor. Between 10% and 15% (ie. 6-9 million) are diagnosed with IBS.
It can be an embarrassing problem that people don’t like to talk about, or people are too busy to go to the doctor and hope it will just go away, or that it might be a bug or something they have eaten.