Interesting blog bits

1. Kyle Almond asks Just how big is 7 billion?
2. Ed Dolan asks Can Spaceship Earth Carry Seven Billion Passengers, and More to Come?
3. Mario Rizzo notes there are Seven Billion People and Counting
4. Tim Harford on Malthus’s ghost and baby number 7bn
5. Matt Ridley writes on Coping with only six billion