Accident rates

What are accident rates?

Counting accidents is not enough to determine whether a company is safe or not: ten accidents in a company of fifty people do not mean the same as ten in one of five thousand. Accident rates solve this problem by relativizing the number of accidents and their severity in relation to exposure, allowing for comparisons of an organization’s evolution over time and its position relative to the sector. INSST Technical Prevention Note 1211 (2024), which updates the long-standing NTP 1 on workplace accident statistics, establishes the definitions and reference formulas, aligned with the criteria of the International Labour Organization.

The rates are calculated from accidents reported through workplace accident reports, typically those occurring during working hours and resulting in sick leave, distinguishing between commuting accidents, which are analyzed separately. Official statistics from the Ministry of Labor and Social Economy publish incidence rates by sector, autonomous community, and severity, and use them to identify the sectors with the highest accident rates and to inform the Labor Inspectorate’s campaigns.

As outcome indicators, indices measure what has already happened. Their preventive value depends on their disaggregated analysis (by center, section, shift, type of accident, form, and material agent), their comparison with appropriate benchmarks, and their combination with proactive indicators: reported incidents, inspections carried out, measures implemented, training provided, or audit results.

Main indexes and formulas

• Incidence rate. Number of accidents resulting in lost work time divided by the average number of people exposed, multiplied by one thousand (per thousand workers) or by one hundred thousand in official statistics. This is the rate published by the Ministry of Labor and is the most appropriate when hours worked are unavailable.
• Frequency rate. Number of accidents resulting in lost work time divided by the total number of hours worked, multiplied by one million. This is the international benchmark rate, as it takes into account actual exposure; commuting accidents and hours not worked should not be included.
• Severity index. Number of days lost due to accidents resulting in sick leave divided by the total number of hours worked, multiplied by one thousand. Lost days are calculated in calendar days and, in accidents resulting in permanent disability or death, using conventional scales of days charged.
• Average duration of absences. Lost workdays divided by the number of accidents resulting in absence; expresses the average severity of each accident.
• Other indicators. Fatal accident incidence rate, frequency rate of accidents without lost time, occupational disease rate, absenteeism rate due to occupational contingencies, and specific rates by type of accident.

Use and interpretation

• Comparison with the sector. Contrast with the incidence rates published by the Ministry of Labor for economic activity, taking into account the differences in method (per thousand versus per hundred thousand, with or without in itinere).
• Time evolution. Series of at least twelve moving months to avoid conclusions based on random variations, especially in small companies where a single accident greatly alters the index.
• Disaggregation. By center, department, shift, seniority, type of contract, form and material agent, to locate the sources of risk.
• Bonus. The incentive system of Royal Decree 231/2017 for companies that reduce accident rates uses general and extreme accident rates calculated on contributions and benefits.
• Complementary indicators. Incidents, unsafe acts and conditions observed, measures implemented, training, inspections and compliance with planning, as proactive indicators.

Organizational application: how to use indexes

1. Define the calculation procedure: sources (accident reports, time records), inclusion criteria (with or without in itinere, with or without sick leave) and periodicity.
2. Record all accidents and incidents with their coding (form, material agent, deviation, injury) and the hours worked by center and section.
3. Calculate monthly incidence, frequency and severity rates, with annual cumulative and twelve moving months, by center and section.
4. Compare with the sector indices published by the Ministry of Labor and with internal objectives, applying the same calculation criteria.
5. Analyze the deviations with the prevention service and the worker safety representatives, and link them to causes and measures.
6. Supplement with proactive indicators and present the dashboard to management and the health and safety committee.
7. Review the objectives and the system of indicators annually.

Preventive management software automatically calculates the indices based on recorded accidents and hours worked, allows them to be broken down by center, section or shift and integrates them into dashboards with preventive activity indicators.

Limits and common mistakes

1. Compare indices calculated with different criteria (per thousand versus per hundred thousand, with or without in itinere, theoretical versus actual hours).
2. Draw conclusions from monthly variations in small templates, where one accident greatly changes the index.
3. Setting index targets that discourage reporting of minor accidents and incidents.
4. Using only outcome indicators without measuring preventive activity.
5. The data is not broken down, which hides the risk areas of certain sections or shifts.
6. Omit occupational diseases and accidents without sick leave from the analysis.

Official statistical formulas and criteria may be updated; NTP 1211 and the methodological notes of the statistics of the Ministry of Labor should be consulted.

Regulatory and reference framework

• NTP 1211 of the INSST . Accident statistics in the company (2024): definitions and formulas of the indices.
• Statistics on workplace accidents from the Ministry of Labor and Social Economy . Official incidence rates by sector, severity, and territory.
• Law 31/1995, articles 16.3 and 23. Investigation of damage to health and registration of accidents and occupational diseases.
• Order TAS/2926/2002, of November 19. Work accident report forms, source of data.
• Royal Decree 231/2017, of March 10. System for reducing contributions for occupational contingencies for companies that have considerably reduced workplace accidents.

The International Labour Organization publishes guidelines on occupational injury statistics that harmonize international definitions; in Colombia, Resolution 0312 of 2019 sets minimum indicators of the SG-SST, including the frequency, severity and mortality of accidents.