移動経歴グラフの分析 : 合衆国都市での調査資料を用いて
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概要
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From the view point of ‘migrations in ones life history’, entire migration careers should be considered. A migration career means a sequence of moves an individual has experienced throughout ones life. Conditions of migration careers would give important clues to deeper understanding of migration behavior. Unfortunately, many of the previous longitudinal data of migration histories were too fragmented to clarify entire patterns of individual migration careers. Therefore, an analysis of migration histories, using more suitable materials, is necessary. In this paper, based on my field survey, I investigated American mobility, through description and classification of migration careers. Statistical methods for the procedures were proposed.Field survey and subjects:This field survey was conducted in two small university towns, one on the West Coast and the other in the East South Central States-Santa Barbara, CA, and Lexington, KY (Fig. 1). Materials on the migration history were collected through interviews with 126 subjects (48 in Santa Barbara and 78 in Lexington). The subjects had the common characteristic of being ‘White Anglo-Saxon Protestants and belonging to an upper middle or middle class’.Statistical procedures:1) Migration-career graph-A migration career can be drawn as a graph which has the horizontal axis representing age and the vertical axis representing the number of moves. 8 examples were shown in Fig. 4.2) Transit vector-I proposed a transit vector [θ1, θ2, θ3, θ4] to abstract geometrical features from a migration-career graph, Change of mobility through ones life course can be summarized as elements in a vector. θ1 indicates mobility (moves/years) in an age-bracket of 0≤<18. In the same way, θ2 is for 18≤<40, θ3 for 40≤<60, and θ4 for 60≤<90. Each θ is assigned to an integral value from 0 to 9. For example, 0 indicates 0 moves/the whole period, and 9 more than 1 move/a year. If a subject is younger than 40, his (or her) transit vector is expressed as [θ1, θ2, -, -]3) Classification-index-The combination of θ1 and θt was a simpler classification-index than the transit vector itself. θ1 represents an initial status of a migration-career graph. θt means mobility through ones life (total moves/ones entire life (years)), and it closely relates to θ2 (R=0.79). For most of the subjects, θ2 has the highest value among the four vector elements. Due to these reasons, the index works in graph-grouping very well (Fig. 7).Findings:a) The subjects have high mobility. Numbers of moves experienced in ones life time were distributed in the range of 2-35, and the mean was 12.12. There were two-groups, a lower-mobility group of about 10 moves and a higher-mobility group of about 17 moves (Fig. 2). The ratio of these two groups was around 7:3. These groups could not be characterized by region nor gender. No significant differences were found among generations (Table 2).b) As a result of transit-vector reduction, the following typical pattern of migration careers was detected: [θ1<θ2>θ3≥θ4=0 or ≥1] (Fig. 5 and Table 3).c) Younger generations have higher mobility than older ones have. The rise of mobility during the age-bracket of 18≤<40 causes the change (Fig. 6).d) The percentage of intra-urban migration has been increasing. Most of all the moves were carried out within a fairly small sphere.
- 人文地理学会の論文