Identify your Needs

Labour is expensive. We need to keep the number of employees to a minimum. Which is the mimimum number of employees we need for each week day and time ?

Administration, military, industry and health sector

For some sectors, it is pretty easy to get the right figures. Say we have an factory where machines produce 300 parts an hour and must be served by 2 workers.

Using sales forecasts we set production to X parts/month.

Using paper and pencil we easily get to know the exact number of shifts and/or machines we need to use.

We can go for

  • 21 shifts= no. 3 8h shifts for each day of the week
  • 14 shifts= no. 2 8h shifts E+L for each day of the week, skipping the night shift
  • 17 shifts= no. 3 8h shifts MON to FRI, 2 shifts on SAT, no shift on SUN
  • etc

This is the basic result, which only depends on production targets.

However we still need to take into account costs and – in the broad sense - employee satisfaction.

When we take into account costs, we find that night and holidays hours cost considerably more than regular work hours.

We could decide to buy a larger number of machines and reduce the number of night and holidays shifts.

When we carry in employee satisfaction, we must remember that any choice re scheduling must meet the ok of unions.

Unpleasant work conditions will increase turn over, which has a cost.

Worked weekends strain social life. Shifts starting at 6:00 am will require the use of the private car. Night shifts have a few fans, but are hated by most people. Badly designed rota will affect circadian rhythm and increase the frequency of sick leaves.

Say we finally come out with a plan like this

E - 4 4 4 4 4 2
L - 4 4 4 4 4 2
N - 2 2 2 2 2 -

How many workers do we need and which rota can we assign ?

Say that the contract we use says 40h/week.

In 1 week we have to cover 54 * 8= 432h

Need of workers = 432/40= 11. Right ?


Each worker is entitled to a number of vacation days and leave days that lower the 40h/week figure.

Absenteeism makes that figure even lower.

An exact calculation is easily done, but as a rule of thumb we need 30% more staff than the theoric figure: this would mean 14.

And note that this was the easy case...

In the case of dock workers, it is almost impossible to forecast the need of workforce. Ferries make for a fixed workload, but most ships enter the harbour with an unpredictable frequency.

Schedule is usually done on a day by day base or even on a shift by shift base.

Those workers are called in who worked at the most distant date.

It is tough for a regular company pay salaries to a fixed number of employees. How can the company be profitable in a drastically changing scenario ?

This is why worker cooperatives are usually active in the harbours.

Worker cooperatives pay flexible salaries: they share the earnings at the end of the month. If many ships entered the harbour and business was good, salaries will be high. If few ships entered the harbour and business was bad, salaries will be dim.

Retail sector

Retail is the most developed sector in terms of planning. A lot of research has been done in order to find the optimal number N of personnel to serve a shop.

We can quickly find an upper bound for N.

We start with the average weekly income (cash registers will give that), say 50,000€.

Managers know the average markup so we get the weekly earning before costs.

Managers know (they decided it at budget time) which percentage of earning will be used to cover costs.

Also they know the personnel cost as percentage on the total of costs.

If we introduce the average weekly cost of 1 assistant, we get to know the maximum number of assistants we can afford, N_up.

We used the index of profitabily here. As we know by now, we need to check the index of service, too. This will give the lower bound for N.

We start with the average weekly number of visitors. This time we cannot use the cash registers, which only give the figures of sales. We take data from turnstiles or photoelectric cells installed at the shop entrance.

Managers know how many minutes of service (in average) a visitor needs. Managers know this figures. This is why managers are so well paid.

Anyway it is no magics: for several days managers had plain clothes technicians study the behavior of customers inside the shop.

All in all we quickly get the minimum number of assistants needed to provide a decent service to incoming visitors, N_lo.

Hopefully is N_lo

Managers are well paid because they must take dangerous decisions.

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