Method of analysis
To compare different generations at the same particular age, we require traffic accident data that covers a fairly
long-term period. This section is based on ITARDA's statistical study database for the past 25 years from 1984 to 2008, with the numbers totaled for every five years in order to ignore small variations. Here again, the figures for males and females are shown separately because of such differences as the average age of license acquisition and the cause of accidents.
Figure 4 shows the share of car drivers among all those directly involved in traffic accidents, i.e., drivers of cars, motorcycles, bicycles and other vehicles, as well as pedestrians, for each age group. Five-year periods such as
"2004-2008" represent the year when the accident occurred (accident year). Usually, only the red line, the latest data, is shown in statistics. What the red line tells us is that car drivers are less frequently involved in accidents as they become older: after 60-64 years old for males and after 50-54 years old for females, and at first glance it can be concluded that this coincides with their retirement from driving. If we compare all five lines starting from 1984-1988, however, we can see that the lines shift to the right along with the passing of the accident year. From this, we can infer that the smaller number of car accidents involving elderly drivers is the result of fewer license holders among those generations, not the result of reaching an age that makes them stop driving.
Moreover,those who were 60-64 in 1984-1988 were 80-84 twenty years later in 2004-2008 and there is virtually no change in their chance of being involved in a car accident, as shown by the black line, in spite of aging. This suggests the desire to continue driving for greater mobility however old they become, or a situation in which they must continue driving.
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Let's look at the same data in terms of number (Fig. 5). Note that the age group 18-19 has a very small number because only two years (18-19) are covered since a license can only be obtained from age 18.
For males, we can see a relatively high risk of being involved in an accident only for the age group 35-39 in the accident year 1984-1988 compared to other age groups. If we explain this from the standpoint of age, e.g., car drivers are more likely to cause accidents at this age, then all generations must show the same trend at this age. However, in the accident year 1989-1993, a distinctive peak can be found only at the age group 40-44, and similarly, the lines for
1994-1998, 1999-2003 and 2004-2008 have a second peak at the age group 45-49, 50-54 and 55-59, respectively, shifting to the right. In other words, as the accident year shifts to the next five-year period, the age group comprising a large population also shifts to the next five-year group. If such a shift is observed, it means that the large number of involved drivers seen in a particular age group reflects a generation-specific factor rather than an age-related factor.
In this case, the generation in question is the baby boomers.
The same is true for females, except for a more marked increase from 1984 through 2003 than in the case of males.
This is not because females of this generation tend to cause more accidents with aging, but presumably because many of these drivers obtained their license in midlife, unlike males who tend to learn to drive while young, and consequently, the total number of license holders had increased over time. If the line shifts to an older age group retaining its shape (in this case, a mountain-shaped line) irrespective of variations in number like in this case of female baby boomers, we can say that this reflects a generation-specific factor.
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