Today and tomorrow over a third of the world’s population (around 2 billion people) will be celebrating Christmas1. Traditionally, the holiday season will inevitably feature an exchange of gifts. The sums spent on Christmas gift-giving are huge! For example, in 2018 the expected spending on Christmas gifts in the United States is around 885 USD per person2 – this is about 2.8% of what someone in the middle of income distribution earns per year.

This summer, Russia is again at the epicenter of the world, but this time for hosting the 21st FIFA World Cup football tournament and not for the occupation of its neighboring countries’ territories. The majority of the world’s population is gripped by football fever, and Georgians are no exception. You can see random people on the streets wearing the jersey of their favorite nation. Students attend classes wearing jerseys or football T-shirts.

Do you happen to have some 1.7 trillion USD to spare? Somewhere between 2 and 10% of the Georgian population suffers from a lack of basic access to drinking water (Global High-level Panel on Water and Peace, 2017; The Global Water Partnership and OECD, 2015). Globally, 1 in 4 people will be affected by shortages of freshwater by the year 2050 (United Nations, 2018).

About half of the world’s population are living in cities. Rapid urbanization puts pressure on urban infrastructure and labor markets, also contributes to environmental degradation, and speeds up the instability of construction projects and dwellings. Climate change is yet another cause that will harm the stability of cities. A solid and global plan on how to tackle urban planning is therefore much needed, which is why the New Urban Agenda was endorsed by the UN in 2016.

Have you ever heard about a mysterious law that predicts the size of a city? If you tell me the population of the largest city in a country, I can tell you the size of the second and third-biggest cities. In 1949, George Zipf came up with the simple theory called the rank-size rule, or “Zipf 's law.” Applied to the size of cities, this law says that the second city and following smaller cities should represent a proportion of the largest city.