Among the male employees in a certain occupational group there were 40 cases of myocardial infarction in one year. The table shows the number of male employees according to age as well as the age-specific incidence rates for the male population in the country as a whole.
| Age | Number of employees during the year | Incidence rate for the country (per 1000 person-years |
| 35-44 | 8 000 | 0.5 |
| 45-54 | 2 000 | 4 |
| 55-64 | 2 000 | 9 |
Calculate the standardised incidence ratio for the incidence of myocardial infection for this group of employees in relation to the population as a whole.