What Are Allowances?
Allowances are percentages added to the normal time to calculate the standard time. They compensate for:
- Personal needs: Bathroom, water, stretching (typical: 5%)
- Basic fatigue: Physiological recovery (typical: 4%)
- Variable fatigue: Depends on conditions (0-15%)
- Unavoidable delays: Process interruptions (variable)
Standard Time Formula
Tstandard = Tnormal × (1 + Allowance%)
Example: 10 min × (1 + 0.15) = 11.5 min standard
The Problem: Arbitrary Allowances
In many companies, allowances are assigned arbitrarily:
- "We've always used 15%"
- "We copied the ILO tables"
- "The union wants 20%, we say 10%, we settle on 15%"
⚠️ Consequences
- • If the allowance is too low: unattainable standard times → frustration, conflicts
- • If the allowance is too high: slack times → productivity loss
- • Without data: impossible to negotiate objectively
The Solution: Work Sampling
Sampling allows you to empirically measure how much real time is dedicated to each type of allowance, eliminating subjectivity.
Categories to Sample
🚻 Personal Needs
- • Going to the bathroom
- • Drinking water
- • Washing hands
Typical: 4-6%
😓 Fatigue / Recovery
- • Rest due to effort
- • Heat recovery
- • Break for heavy work
Variable: 4-15%
⏱️ Unavoidable Delays
- • Receiving instructions
- • Minor adjustments
- • Routine cleaning
Typical: 2-5%
☕ Authorised Breaks
- • Lunch (if counted)
- • Scheduled breaks
- • Area meetings
Per agreement
Study Design
To obtain reliable allowances, the study must be:
Duration
Minimum 2 weeks (representing variability)
Observations
500-1000 (margin of error ±3%)
Confidence
95% or 99% (important negotiations)
Coverage
All shifts and days of the week
Example Results
A 4-week study at an assembly plant revealed:
| Category | Observations | Percentage | Interval (95%) |
|---|---|---|---|
| Productive work | 621 | 77.6% | ±2.9% |
| Personal needs | 42 | 5.3% | ±1.5% |
| Fatigue / Recovery | 56 | 7.0% | ±1.8% |
| Unavoidable delays | 30 | 3.8% | ±1.3% |
| Non-productive (avoidable) | 51 | 6.4% | ±1.7% |
| TOTAL | 800 | 100% |
Total Allowance Calculation
Justifiable allowances (excluding avoidable non-productive):
Personal needs: 5.3%
Fatigue / Recovery: 7.0%
Unavoidable delays: 3.8%
Total Allowance: 16.1%
95% confidence interval: between 12.5% and 19.7%
Use in Negotiations
With this data, the engineer can present:
- Empirical basis: "It's not my opinion, it's 800 observations"
- Confidence intervals: "With 95% certainty, it's between 12.5% and 19.7%"
- Breakdown: "Of that 16%, only 3.8% are system delays"
- Identifiable improvement: "The 6.4% non-productive is an improvement opportunity"
✅ Typical Result
Negotiations based on data have 50% fewer conflicts than those based on opinions or generic tables.
Comparison with ILO Tables
ILO tables provide generic ranges based on theoretical conditions. Sampling reveals the specific reality of your operation:
| Factor | ILO Table | Actual Sampling |
|---|---|---|
| Personal needs | 5% | 5.3% |
| Basic fatigue | 4% | 7.0% |
| Delays | Variable | 3.8% |
| TOTAL | ~14-15% | 16.1% |
In this case, sampling revealed that real fatigue (7%) was higher than the table (4%), probably due to specific conditions such as temperature or physical load of the station.