In 2002, the government introduced a performance-related bonus scheme in order to boost teachers' pay and help retain staff. Experienced teachers can apply for a one-off bonus of £2,000. Currently, almost all teachers who apply for the performance pay get it. They can only apply after they have taught for six years. Study suggests performance related pay is inappropriate for teachers However, a recent study has suggested that there is no evidence that paying teachers performance bonuses leads to better exam results or attracts more recruits to the profession. Researchers from the Institute of Education in London found little evidence to suggest the payments had improved results or attracted more people into teaching. The study argued that it is difficult to determine the impact of any one teacher on a pupil's progress. " A pupil may have private tuition, help at home, or any number of external influences. So we may never know objectively whether performance-related pay has positive effects on pupil learning outcomes” said Professor Dalton, a co-author of the study. The researchers even argue that bonus payments could be counter-productive because teachers were used to working together instead of competing with each other. The researchers say it is a "difficult if not impossible task" to devise a performance-related pay system for teachers that makes them work harder and more productively, does not need expensive monitoring, encourages teamwork and discourages teaching to the test. Other countries, including the USA, have paid teachers performance bonuses but the study suggests they provide little convincing evidence for or against performance-related pay.