The paper presents an algorithm for estimating the decrease of the average life expectancy (ALE) as a result of an accident, a catastrophe or a terrorist act, accompanied by human casualties or losses of limb, health. Solution of this problem is absolutely necessary when managing territorial risk by the ALE criterion, as it is crucial for solving such practical vital problems as optimal design, construction, operation and maintenance of interdependent critical infrastructures, harmonizing decision making of local authorities when executing regional governance.
The basis of the model is the initial (unperturbed) table of mortality/survival of the population living in the immediate vicinity (destruction zone) of the critical infrastructure or the potentially dangerous object (PDO). The population of a district, town, municipality, region/territory or country is taken as the original cohort that allows evaluating the relative contribution of the accident to the decrease of ALE.
The main specific demographic feature of an accident/ catastrophe/ terrorist attacks is that they occur at random times and may lead to death, injury, disability and hospitalization of an unknown number of people of different sex, age, health and qualification. These events are random disturbances of the basic mortality/survival table that unambiguously lead to an ALE decrease of random value, for any size of the initial cohort. This allows comparing two mortality tables, both compiled for the same population: one before and the other after the accident and thereby estimate the magnitude of the ALE reduction.
The modern theory of demographic statistics is used to determine how many person-years are irrevocably lost due to accidents or catastrophes.
The paper considers three cases: (1) the impact of one person's death on ALE of the cohort in consideration; (2) the effect of the death of several people of the same age on ALE of the cohort in consideration; and (3) the impact of the death of several people of different ages on ALE of the cohort in consideration.