Corruption is not always criminal. Like criminal behavior, corruption hurts people and it causes outrage to victims and those who value civil society. Like criminal behavior, corruption is unethical. Corruption does not feature prominently in the criminal justice literature, and to learn about it students turn to literature in development economics, public administration, law, political science, and business studies. The criminal nature of corruption should be studied so that offender, opportunity, and target can be understood, in order that controls can be put in place. Corruption can and does occur in all spheres of activity, and in all countries. In many countries the criminal justice system is badly corrupted. In others, criminal justice activities are at the forefront of dealing with corruption. Corruption is costly and devastating. The World Economic Forum has estimated that the cost of corruption equals more than 5 percent of global GDP (about US $2.6 trillion). The World Bank has estimated that about $1 trillion per year is paid in bribes; whereas about $40 billion per year is looted by corrupt political leaders.