Are there reliable data to show the prevalence of violence against women and girls?

Understanding the extent, the nature, and the consequences of violence against women and girls is important to inform legislation, policies and programmes. To that end, the EU and UN Member States have made efforts to collect data and compile statistics related to the prevalence of different forms of violence against women and girls, especially domestic and intimate partner violence. The availability of prevalence data on violence against women and girls, however, remains uneven across and within countries. Quality, reliability and comparability of the data across and within countries remain a challenge.

http://www.un.org/en/spotlight-initiative/assets/pdf/spotlight.faq.letter.02.pdf