Workforce Effectiveness is mainly determined by the skill levels of the workforce. However it is also influenced by the motivation levels of the staff.
Note that workforce motivation and skill levels reinforce each other - more training leads to a more highly-skilled workforce, which in turn improves workforce motivation. Increased motivation both reduces staff turnover and signals a good place to work - so the caliber of new employees is higher, leading to a more skilled workforce...
Likewise - less training leads to lower skills and lower motivation, higher staff turnover and lower caliber recruits, which in turn leads to lower skills.