Joseph Bonneau of the University of Cambridge has conducted a study from 70 million Yahoo! users. The data used for the study was protected and he did not see anyone’s private information. From the study, Joseph found that people over age 55 use stronger passwords than those under 25.
This is the case no matter what the country of origin and what the native language of the user is. Even if the credit card information is stored on the user’s accounts, it does not necessarily motivate how strong that the passwords of the users are. The study showed that Germans and Koreans have the strongest passwords, but Indonesians have the weakest. Bonneaus suggests that you choose a nine-digit combination similar to a phone number.