Data classification is a crucial step in creating maps, especially in terms of public interpretation; the way a map looks and how it demonstrates differences in data can completely change the way a user will read it. Different methods have different advantages and disadvantages, some just in terms of practicality (manual breaks is obviously better for a more controlled way of classifying very different data) and some in terms of aesthetics. Natural breaks leaves the classifying up to the computer, which can be easier for the producer; however, it can also create maps where classes look much more dramatically segregated. Equal Interval often does the opposite, and makes the differences between different classes much less obvious. The manual method allows much more creative freedom in terms of how one wants data to be represented, which in turn allows more manipulation for certain reactions (which comes with its own ethics and morals). Each method is useful at a time, but can also be easily manipulated for different scenarios. (refer to ‘data class” PDF below)
Affordability measuring is taking data on income and price of housing to evaluate how ‘affordable’ an area is in terms of housing. It is more useful than simply looking at housing cost because, obviously, without taking into account the income of the buyer, it is hard to know how affordable the cost of a house is (for example, housing in Vancouver is incredibly expensive, but even worse when you take into account the fact that income in the city is relatively low as well on average).
Housing affordability rating categories, as determined by Demographia International Housing Affordability Surveys, range from “Very Affordable”, to “Affordable”, “Moderately Unaffordable”, “Seriously Unaffordable”, and finally, “Severely Unaffordable.” This survey is determined by measuring middle-income housing affordability, using median measures of existing house sales prices and household incomes. This source could be considered “trusted” because they are organized around the idea that housing affordability has drastically decreased in the last few decades, and so we know there is no ulterior motive in terms of expressing affordability.
Affordability is a very useful indication of how ‘livable’ a city is, but it is only one aspect of ‘livability’. Cost of food, health care, education, population density and climate are all examples of other factors that impact how ‘livable’ a city is. (refer to ‘affordability” PDF below).