2000115-Strengthening-Communities-with-Neighborhood-Data

Advances in Analytic Methods for Neighborhood Data 325
the chart is represented in our source analysis by degrees of color, from
dark red (very low) to dark blue (very high). The neighborhood types are
created by grouping neighborhoods that tend to have similar scores on
the same variables, which can be viewed in our report by the concentrations
of red and blue cells on the map. For instance, a blue area on the
bottom left of the map identifies a group of neighborhoods with a high
percentage of young adults, high income levels, and a high concentration
of retail, services, and entertainment venues. Similarly, a blue area
at the top of the central section of the map identifies a group of mostly
residential neighborhoods characterized by older residents, high homeownership
rates, and prevalence of single-family homes.
The figure contains two additional important pieces of information.
The first is that neighborhoods that are closer together in the chart are
more similar than neighborhoods that are further apart. These relationships
are summarized in the tree structure on the top of the figure. In
this sense, the typology generated by the DNT project is actually a taxonomy
of neighborhoods: indeed, it works just like a taxonomy of living
organisms in biology, which organizes all forms of life in a hierarchical
structure that goes from the broadest grouping of kingdom to phylum,
then class, and so forth all the way down to species.
This means that the typology can be used from the top down as well
as from the bottom up. In other words, we can start with the broadest
possible grouping of neighborhoods and further refine our types as
we move down the tree. Or, we can start with a particular neighborhood
and identify which other neighborhoods are most similar to it.
The top-down approach is useful to surface general findings regarding a
particular neighborhood type, such as its likelihood of undergoing particular
changes or the interventions most likely to make a difference.
The bottom-up approach, on the other hand, can be used to see how a
particular neighborhood is doing relative to its peers, or to evaluate the
impact of a specific intervention.
The second piece of information is that the same hierarchical structure
is applied to the variables used to build the typology. Therefore,
variables that are closer together in the figure tend to be correlated to
each other and have similarly high or low values in the same neighborhoods,
revealing how different factors combine to determine neighborhood
types. In particular, the tree to the right of the map shows there
are three main groups of variables. The first group has to do with the
stability of the neighborhood and its housing stock, and it includes