What separates good workplaces from great ones? After 30 years of analyzing happy and efficient companies, Robert Levering, co-founder of Great Place to Work, has a few ideas.

The common denominator, he says, is trust. The three levels of trust for employees are: credibility of management, what does management think of me and knowing there is a level playing field. Evergreen leaders can use Levering’s insights to create an environment where employees are engaged, satisfied and productive.