The intuition is shared by most leaders: a healthy employee works better. But intuition is not enough to justify an investment. The data are what counts. Three major sources, Gallup, the University of Oxford and Saïd Business School, now make it possible to quantify with precision the link between health, well-being and workplace performance.
The Oxford / BT study: +13% measured productivity
In 2019, researchers at Saïd Business School (University of Oxford), in partnership with BT Group, conducted one of the most rigorous studies on the subject. Over a six-month period, they tracked the productivity and well-being of more than 1,800 call-center employees in real time. Result: in the weeks when employees reported being happy, their productivity was 13% higher than in the weeks when they felt poorly.
Unlike retrospective studies, this one measured well-being and productivity in real time, week after week, on the same individuals. This eliminates selection bias and makes it possible to establish a direct correlation between psychological state and operational performance.
Gallup: the impact of disengagement quantified globally
Gallup's State of the Global Workplace Report (2023) provides a complementary perspective. According to this survey of more than 120,000 employees in 150 countries, 23% of workers report being engaged at work. The remaining 77% are either disengaged or actively disengaged.
The cost of this disengagement is estimated at $8.5 trillion in annual global productivity loss. At the scale of a 100-person company, disengagement represents a loss equivalent to 15 to 20 full-time positions. The most cited factors of disengagement? Chronic fatigue, unmanaged stress, and lack of recognition of overall health.
Presenteeism: the invisible part of the iceberg
Absenteeism is visible and measurable. Presenteeism, being physically present but mentally and biologically underperforming, is far less so, and yet represents a cost two to three times higher according to Harvard Business Review studies. An employee suffering from chronic fatigue, untreated pain or sleep disturbances may be present while functioning at 60–70% of capacity.
This is precisely the mechanism that workplace health programs primarily address: not just reducing sick leave, but restoring the biological capacity to perform, energy, concentration, recovery, stress regulation.
In a team of 50 people, if 30% function at 70% of capacity due to fatigue or stress, the effective loss is equivalent to 4.5 full-time positions, without a single day of absence being recorded.