Aoba-ku

In the most recent Population Census the population is about 311,000 (310,756 in 2020). Over the five years from 309,692 in 2015 it added only about a thousand, entering a nearly flat phase. It is one of the eighteen wards that make up Yokohama, the administrative ward in the city’s north. Because it is a ward and not a city, figures of the kind a city carries — the Fiscal Capacity Index or the childcare waitlist — cannot be treated here. What can be read are the indicators that mirror how people are turning over in their living.

First, households with children make up 23.0% (2020), a high level even within Yokohama — a figure mirroring how the ward’s character was shaped as a residential area for households raising children. The absolute number of children, though, points the other way. Those under 15 fell from 42,772 (2015) to 39,002 (2020), some three thousand seven hundred fewer in five years. Over the same period the share aged 65 and over rose from 19.7% to 21.9%. The household-with-children rate stays high, yet the real number of children falls and aging advances — here is the figure of a mature suburban residential area, the generation that moved in all at once aging in place. The residential land price is in the 289,000-yen-per-m² range. Why it takes this shape cannot be read without going back to the origins of the Den-en-toshi Line and suburban development.

Aoba-ku’s skeleton is set not on the natural landform but on a single line a railway company drew. This stretch was originally hill country spreading across northern Yokohama; but for its northwest, it was land of continuing farmland and woodland with no large industry. That a block of undeveloped, rolling, unbuilt land remained near the center is the very geographic condition that decided this town’s fate.

The first foundation is the railway. In 1966 the Tokyu Den-en-toshi Line opened, and the ward’s stations opened in succession. In step with this, the “Tama Den-en-toshi” development led by the Tokyu Corporation went into full swing. Laying the railway first, then developing the trackside hills areawide as residential land, is the textbook form of suburban development by a private railway. In the terms of economic geography, it is a structure in which a commuter line into the center planfully produces the suburbs where commuters will live. Once a single axis toward the center was drawn, hills that had been farmland and woodland began at a stroke to hold value as residential land.

The second is the administration’s following of the population growth that development set off. Taking in the sharp population rise from trackside development, in 1969 the northwest of Kohoku Ward was first split off as Midori Ward. Then in November 1994, that Midori Ward and Kohoku Ward were reorganized, and Aoba Ward and Tsuzuki Ward were newly established. Most of Aoba Ward was carried over at this point from the area of the former Midori Ward. The railway bred the suburbs, and the increased population had the lines of the administrative wards redrawn — this town’s shape stands, more than on landform, on the origins of railway development and the ward divisions that chased it.

What characterizes Aoba-ku is that, while it holds a household-with-children rate of 23.0%, high even within the city, the absolute number of children fell by some three thousand seven hundred in five years. This is no contradiction but a time lag common to suburban residential areas developed all at once. The households that moved in when the trackside lots along the Den-en-toshi Line were put on the market areawide age in place in that same town. The children of that time grow up and leave, and the parent generation shifts into the elderly layer. As a result, the town’s character as “rich in households with children” lingers a while, even as the real number of newly born children thins.

That the share aged 65 and over rose from 19.7% to 21.9% is another face of the same single flow. A town where the wave of moving-in came at once meets the wave of aging at once too. The present face of a high household-with-children rate and the present face of falling children and advancing aging are not separate facts; they branch from one origin — “the generation that moved in all at once is aging together.” Read the same “children decreasing,” and its meaning differs entirely from the thinning of a depopulating city. Set the high household-with-children rate beside the fall in the real number of children, and only then does the time lag — one cohort aging together — come into view.

Aoba-ku holds a function of its own. One is the trackside residential land pierced by the Tokyu Den-en-toshi Line, much of the ward lying in the “Tama Den-en-toshi” area. The structure in which rolling hillside lots spread atop a single commuter axis toward the center all but decides this ward’s character. The Tomei Expressway and National Route 246 run along the ward’s east side, supporting, with the railway, the lines of movement toward the center.

Aoba-ku is one of the administrative wards making up the city of Yokohama, not a city in itself. It is the side of Yokohama (14100), a Designated City, that holds powers on a par with a prefecture; the ward is the unit that carries, in deep color, the character of a residential area. From hills that were farmland and woodland, to the garden city a railway company drew, and on to a mature suburban residential area — the condition that “a block of undeveloped hills lay near the center” summoned a single railway, and that railway filled in the town. Rather than following the natural landform, a man-made axis — a commuter line — rewrote farmland and woodland into residential land. The order in which the railway came first and the town clung on after is the premise of every figure in today’s Aoba-ku.