Why GDP per capita (PPP) ?
GDP per capita (PPP) is a convenient number to use as a way to measure average quality of life.
Other variables may prove more effective; I suggested this specific one for a few reasons:
Familiarity
It is well known variable that is available for many countries,
and is a variable that government leaders are not only familiar with,
but usually have a vested interest in raising for their own political purposes.
Unifying Focus Towards a Common Goal
I saw it as an opportunity to attract the attention of not only NGO's and international organizations,
but also the political leadership and individuals within the community.
Since having multiple variables could cause more confusion and open the possibility of conflicting agendas, it seems like a good way to focus all stakeholders towards a common goal.
Given that the actual projects may only be focused on variables that merely correlate with GDP per capita,
such as health, fertility rates, and literacy - one may ask why the goal would not to be simply to focus on those variables instead of trying to tie them into GDP per capita.
The idea is that if any one particular project looks like it may conflict with other agendas that the stakeholders have.
It allows for more flexibility to shift the attention to other projects (ex: infrastructure or health care vs fertility education), while still making progress on the overall objective, which is to improve quality of life.
Good Measure of Standard of Living
It does appear to correlate well with other variables that are typically associated with quality of life.
ex: infant mortality, education levels, etc..
My personal experience in various parts of the world led me to develop my own subjective, qualitative intuition as to
what the relative quality of life was for any particular place I visited.
Once I had a list of places ranked by quality of life in my head,
I researched around the web for lists of countries ranked by a single economic variable.
GDP per capita (PPP) struck me as the closest way to reproducing this ranking in my head.
The list ---> http://en.wikipedia.org/wiki/List_of_countries_by_GDP_(PPP)_per_capita
Economic variables that correlate with GDP per capita (PPP)
Oil consumption +76
May also be negative at times, but still highly correlated.
http://cvjugo.blogspot.com/2008/03/gdp-per-capita-and-oil-imports-strong.html
This is a good measure of the industrial progress of a country.
Projects that should impact this variable: traditional capital investments, manufacturing, infrastructure, etc..
Life Expectancy + 0.63
Does not correlate above 30,000 (GDP pc) because life expectancy appears to caps out around 78
http://www.indexmundi.com/g/correlation.aspx?v1=67&v2=30&y=2003
Projects that should impact this variable: targeting health care, such as AIDS, water quality, etc..
Total fertility rate -0.55
Varies with GDP per capita, -0.79 for <>
suggesting that high fertility rates are bad for poorer societies, but good for wealthier ones.
http://www.indexmundi.com/g/correlation.aspx?v1=67&v2=31&y=2004
Projects that should impact this variable: women's rights, fertility education, women's health, planned parenthood
Literacy + 0.55
Does not correlate above 30,000 (GDP pc) because literacy caps out at 99%
http://www.indexmundi.com/g/correlation.aspx?v1=67&v2=39&y=2003
Projects that should impact this variable: education initiatives - English, Math, Science, etc..
HDI +0.77
Human Development Index - mathematically combines life expectancy, literacy rate,
and GDP per capita into a single variable.
http://www.erin.utoronto.ca/~w3psyuli/WellBeingScience/WellbeingHDI.htm
list of countries by HDI
http://en.wikipedia.org/wiki/List_of_countries_by_Human_Development_Index