What is attrition rate?
Attrition rate is the percentage of employees who leave an organisation over a period. SHRM calculates it as departed employees divided by total employees, multiplied by one hundred.
In everyday use, attrition and turnover are often used interchangeably. SHRM draws a distinction: attrition is a gradual reduction through retirements, resignations or eliminated positions that are not backfilled, while turnover covers departures that are usually replaced.
Why does attrition matter in tech and engineering teams?
Because knowledge leaves with people. In a team that maintains a complex system, each departure takes with it context that is not written down, and the replacement needs months to rebuild it.
It also feeds recruitment directly. A team with high attrition spends a growing share of its hiring effort replacing people rather than growing.
How is attrition rate different from retention rate?
They look at the same population from opposite ends. Attrition counts who left during the period. Retention rate follows a group present at the start and counts who is still there at the end.
The difference matters when the team changes during the period. A team that hires many people and loses many new joiners can show acceptable attrition and poor retention of the people it actually invested in.
What does attrition rate reward, and what can go wrong?
Low attrition is usually read as good news, which pushes managers to avoid departures at any cost. Some departures are healthy: a role that no longer fits, a low performer leaving, a person moving on after delivering what they came for.
Attrition counts who leaves, not who you lost. The useful version separates voluntary from involuntary departures and looks at who left, especially among recent hires. Early departures are often a recruitment signal, linked to the job description or to promises made at the offer stage.
