Methodology for the Cities Ranking
We constructed the city index based on eleven variables. These eleven variables capture a city’s local “greenness,” and some also measure whether a city is a “good citizen.”Each of the eleven variables is standardized to create mean zero, standard deviation equal to one variable. We assign a weight of .05 to nine of the variables. These include garbage production per capita, the price of gasoline, the price of electricity, the share of public employment in sanitation, recycling laws, the share of land devoted to parks, private vehicles per capita, public transit’s share of total energy consumption, and smoking laws. We assign a weight of .20 to a city’s per-capita income level and we assign a weight of .35 to its particulate matter level. Particulate matter receives a higher index weight due to the immediate morbidity and mortality effects associated with exposure to this pollutant.
This eleven-variable data set is based on three data sources. The Reader’s Digest Survey provides information on city environmental laws, energy prices, garbage production and sanitation employment, and city park space. The transportation data was provided by Jeff Kenworthy and Felix Laube, 2001, The Millennium Cities Database for Sustainable Transport. And the particulate matter data source is the World Bank’s Development Economic Research Group Estimates.
Methodology for Countries Rankings
To build our green and livable index, we collected data from the United Nations 2006 Human Development Indicators (HDI) and the 2005 Environmental Sustainability Index (ESI). The HDI examines national quality of life and doesn’t merely focus on per-capita income. It takes into account information on life expectancy, educational attainment and national per capita income. The ESI index is based on a collaboration between Yale University and the Center for International Earth Science Information Network at Columbia University, and the World Economic Forum. It tracks a diverse set of indicators that influence environmental sustainability at the national level. For 141 nations, the database offers information on 76 different variables organized into 21 sustainability categories. We included information on 13 of these 21 categories in our index. Six of the thirteen categories have a direct effect on a nation’s daily environmental quality of life, such as air and water quality. The remaining seven categories are key indicators of whether a nation is a good regional and global “citizen” in not exacerbating environmental challenges. Such a nation does not contribute to regional problems such as acid rain, and on the important issue of climate change, has a small ecological footprint and produces relatively few greenhouse gases. A good global citizen also protects biodiversity located within its physical borders. To construct a national ranking based on a nation’s HDI score and on its scores on each of these thirteen categories, we first take all fourteen scores and standardize them. This transforms the data into comparable units. We chose to give the HDI index a weight of 50%, and the subset of ESI variables received a weight of 50%. We weighed each ESI variable equally so each of the thirteen indicators receives a weight of (1/26). Sorting this overall score provides our ranking.Standardization Formula Used:
Define Xi = nation i's score on variable X
Define Xbar = the sample average for variable X
Define sdX = the sample standard deviation for variable X
Nation i's standardized score = (Xi - Xbar)/sdX