What percentage of people who try to quit drugs cold turkey are successful?

Cold turkey means to stop smoking with no gradual reduction i.e. you give your system a short sharp shock as smoking stops and nicotine is withdrawn from your system. Quitting smoking cold turkey does not have a high success rate, due to the extreme symptoms that nicotine withdrawal causes, and most of them start smoking again. It works for people who are strong willed and also beneficial as the withdrawal symptoms are only there for about a week and the nicotine is out of the system in a month. The success rate of this method is about 1/3 rd.