In the health sector the ability to work in the usually better resourced and remunerated, private sector deters migration, although enabling such opportunities has been resisted where it is seen to divert doctors away from public responsibilities and areas of particular need. Tonga, where additional private practice is permitted for public sector doctors, has retained them more successfully than neighbouring Samoa, where this is not allowed. Larger numbers of doctors and nurses migrate but the more critical migration is of the relatively few allied health workers, and of those with such skills as anaesthesiology. ( Nonetheless, many countries have sought to raise salaries for skilled workers and have used particular strategies involving overtime and similar payments to achieve more effective recruitment, retention, geographical distribution and skill mixes.