Masonry Magazine July 1969 Page. 29
Overtime and Inefficiency
Here's an example that illustrates the relationship between overtime and inefficiency.
Conditions:
1) 20,000 man-hours of straight time (five 8-hour days) estimated for the job.
2) $6.00 per man-hour wage rate before taxes and insurance.
3) Overtime at double time.
Problem:
With the above conditions, what is the additional cost to do the job on the basis of six 10-hour days instead of five 8's?
Answer:
Six 10's 60 man-hours or 40 hours straight time
40 hours pay
20 hours overtime
40 hours pay
60 hours worked
= 80 hours pay
80
60 1.33 multiplier, if no loss of efficiency is considered. However, based on the Detroit survey (Table 1) let us assume 17 per cent inefficiency for six 10's. Therefore, 1.33
.83 1.6 multiplier
20,000 man-hours @ $6 per man hour equals $120,000
X 1.6
$192,000
Less $120,000 original cost
$ 72,000 increased cost
Thus it cost $72,000 additional to do the work in six 10's instead of five 8's.
If the owner picks up the overtime wage premium, the contractor still stands to lose: $ 72,000 increased cost
Less: $ 39,600 overtime paid for by owner
$ 32,400 loss due to inefficiency.
Some of the men are satisfied, basically, with 35 hours. If you have them working a 40 hour week, they take a day off and still make as much money as they would for a normal 35 hours.
Bob Hydon had a similar experience. "When a project is accelerated to a large amount of overtime, say 6 or 7 days a week, many men do not show up on a Monday or a Monday and a Tuesday. This means that if you have planned your work for 40 men, you may need 45 men on a job-and that is a waste of manpower. We have a rule of thumb of 10 per cent over-ride on the manpower on a job. To get 40 men on the job we need 45 men's names on the roster."
Mental attitude is quite similar to the problem of fatigue. Some men pace themselves to put out only so much work, regardless of the number of hours they are on the job. Also some workmen tend to feel that the overtime is merely a bonus arrangement for them and that they are not really expected to produce more than normal.
It appears to be common to have a large turnover of men when there are many overtime jobs in progress at the same time. "I have found that the turnover on any job over a period of six months would run 30 to 40 per cent," said Mr. Harlan. "You start a job with 20 men. By the time you end the job you have only half of those men with you throughout the entire job. That's a large turnover."
Long working hours bring on both physical and mental fatigue, and this causes the errors to multiply. The errors must be corrected, which means doing a job more than once and adding to the inefficiencies of an overtime job.
Was the Detroit survey too conservative or not conservative enough?
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