I want to know the answer to the following question:
What percent is the  failure rate of contraceptive pills?
All the background I'm provided with is that "In cases where antibacterials have been suggested to affect the efficiency of birth control pills, such as for the broad-spectrum antibacterial rifampicin, these cases may be due to an increase in the activities of hepatic liver enzymes' causing increased breakdown of the pill's active ingredients.". Is that enough to answer the question?
Answer: no