Calculation
The standard formula is:
Absenteeism Rate = Sickness-related Lost Hours ÷ Planned Contracted Hours × 100
Working days are frequently used instead of hours. While simpler to administer, using days can distort results where working patterns or part-time arrangements vary across the workforce — an absence day for a full-time employee represents more lost working time than one for an employee contracted for 20 hours per week.
What Should Be Included
The rate is only meaningful when clearly defined. It should encompass periods of incapacity for work, including certified and self-certified statutory sick leave, medical appointments relating to ongoing incapacity, and occupational health rehabilitation.
It should not include statutory annual leave, bank/public holidays, family-related leave (such as maternity, paternity, or shared parental leave), study/training leave, unpaid leave, or periods of contractual lay-off/short-time working. These represent planned or statutory entitlements and belong, where monitored, within a broader, separately calculated overall absence rate.
Limitations of the Metric
A low absenteeism rate is not automatically a positive indicator; it can disguise presenteeism (employees working while unwell) or leaveism (using annual leave to cover illness).
For UK employers, more actionable insight is gained from monitoring:
- Historical trends and departmental benchmarks.
- The distinction between short-term persistent absences and long-term sickness absence (often monitored using metrics like the Bradford Factor).
- Underlying workplace factors, such as work-related stress or health and safety risks.
Data Protection & UK GDPR
Under the UK General Data Protection Regulation (UK GDPR) and the Data Protection Act 2018 (DPA 2018), health data constitutes 'special category data' requiring strict processing safeguards.
In line with the Information Commissioner's Office (ICO) Employment Practices Guidance:
- Absence reporting and analytics must remain aggregated and anonymised so that individual employees cannot be identified.
- It is standard practice to establish an aggregation threshold (typically a minimum cohort of five to ten employees) below which absence rates are not reported.
- Employers must record only what is necessary for statutory and payroll purposes (such as Statutory Sick Pay (SSP) administration and fit notes) and must not process or store sensitive underlying medical diagnoses without a valid lawful basis and condition under Article 9 UK GDPR.
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