There are two main sources that are used to measure crime levels in England and Wales: 1) Official statistics which are crimes reported to and recorded by the police. These provide information on annual crime patterns and trends over time. 2) The British Crime Survey which collects information on crimes whether reported to police or not through interviews with members of the public. This helps account for the "dark figure of crime". 3) Both sources have strengths and weaknesses in providing a full picture of crime levels. The official statistics only include reported crimes while the survey depends on accurate self reporting.