The type of unemployment that economists find most concerning is a

Structural unemployment

While the frictional unemployment can be tackled by increasing the number of job matching agencies, nothing can be done about voluntary unemployment because those who are not willing to work are not a part of labour force as well. cyclical unemployment is temporary and it is present only when the economy is out of the full employment level so it is a short term problem. Structural unemployment is a long-term problem and it is the most difficult to reduce. this is because it results from structural changes in the economy in which old skills become obsolete and strong resistance come from those skilled workers whose skills are now outdated. Therefore, economists believe that it is a complex task to maintain the same skilled labour force.