Globally, one in two employees know what is expected of them at work. That means half of employees worldwide are unsure about their roles, according to Wellbeing at Work: How to Build Resilient and Thriving Teams, by Jim Clifton, chairman and CEO of Gallup, and Jim Harter, PhD, Gallup's chief workplace scientist.

Even worse, the authors note, those employees are stressed and anxious -- even losing sleep -- because they don't know what their boss wants from them. Half don't know if they're succeeding or failing. This damages their career well-being.

Those who report unclear expectations at work also report higher daily worry, stress, anxiety, and loneliness.

On the other hand, those who say they have clear expectations at work are 26 percent more likely to be thriving in their overall lives.

The performance implications are substantial. By increasing the ratio of employees who know what's expected of them from one in two to eight in 10, organizations can realize a 22 percent reduction in turnover, a 29 percent reduction in safety incidents, and a 10 percent increase in productivity.

Clear expectations are an employee's most fundamental need

Without them, no corporate program, initiative, or culture can succeed. However, many veteran leaders and established companies don't get this right. Fewer than half of employees (43 percent) strongly agree that they have a clear job description, and even fewer (41 percent) strongly agree that their job description aligns with the work they do.

The employees who strongly agree that their job description aligns with the work they do are 2.5 times more likely than other employees to be engaged. But the greatest pitfall of the first engagement item is that managers assume there's a simple solution: "If people don't know what's expected, I'll just tell them."

Getting employees to understand what's expected requires much more than telling them what to do. Employees need to understand the fundamentals of their work, which include but are not limited to their job description.

In today's highly matrixed workplace, employees are often on multiple teams with various team leaders who have many different priorities. While these employees may report high levels of collaboration and get along with their colleagues, they still don't know what to do first. This creates anxiety and stress.

Even worse, managers are typically less clear about expectations than their employees are.

In many cases, state the authors, employees and their managers are being held accountable for work that may or may not correspond with the work they're being evaluated on. For this reason, one of the most important roles in management is to provide meaningful feedback multiple times a week -- once a week at a minimum -- through check-ins, quick connects, and developmental conversations. Central to these meetings is discussing goals.

Clifton and Harter share these science-based insights as guidance for giving your employees clear expectations:

Set clear goals

A meta-analysis of 74 studies published in Journal of Management found that clear, less ambiguous goals for an individual's role were related to increased productivity. Another meta-analysis of 49 studies published in Journal of Applied Psychology found that specific and difficult goals were associated with higher performance. Even moderately difficult goals were associated with higher performance as long as they were not ambiguous.

Provide adequate resources

A meta-analysis published in Journal of Vocational Behavior found that difficult goals can cause burnout if employees don't have the supporting resources to do the work.

​Lead collaborative goal setting

Gallup has found that just 30 percent of employees strongly agree that their manager involves them in setting their goals at work. But those who do strongly agree are 3.1 times more likely than other employees to be engaged.

Nurture collective intelligence

The authors point to numerous studies that show the importance of individuals knowing how their roles relate to their teammates' roles. Team members gain "tacit knowledge" or "shared cognition" as they work together over time. Individuals progressively get better at anticipating how their team members respond in various situations. They can also get better over time at retaining this information and applying it to new situations.

"Clear expectations" may sound basic, but when you apply them consistently, they are deeply gratifying to employees. When a manager and employee set goals and clarify expectations together, it is motivating. It spurs ownership, action, creativity, and innovation -- because everybody determines the goal.