Figure 4a and 4b are plotted by Qin Liu (qinliu.christoph@gmail.com).

Comments on .csv files;
- Global_pop.csv contains population data for all countries, which is same with Population_(Millions).xls in /Raw Data but has deleted data for regions and replaced all 'NA' by 0s.
- Global_ectot.csv contains energy consumption data for all countries, which is same with Total_Primary_Consumption_(Quadrillion_Btu).xls in /Raw Data but has deleted data for regions and replaced all 'NA' by 0s.
- Global_ecpercap.csv contains energy consumption per capita data for all countries, which is calculated using Global_pop and Global_ectot. Consumption Per Capita for A=(Energy Consumption of A)/(Population of A).
- Figure_4b.csv contains empirical population data and theoretical population data. Theoretical data are calculated in an engineering calculator OpenLu (Download url: http://www.forcal.net/xiazai/lu1/openlu32.rar) by solving y=x+(1-x)*ln(1-x) with input y (cumulative energy consumption).
