31 that regional/local governments emulate each other in implementing similar policies.

# **7. Conclusion**

Maps have been a major innovation in human history, contributing to nation building and trade globalization. Historically, maps showed the world in 2D. Given historical transportation and building technologies, human life itself was mostly functioning on a horizontal plane. With the advent of airplanes or skyscrapers in cities, our world verticalized. Today, satellite imagery and computer technology allow us to generate a detailed 3D picture of our global built environment.

The outcomes of this global 3D study of the building stock expand the body of research in this area. We have found that economic development accounts for two-thirds of international volume differences, with the remaining third probably due to policy-related factors. While Asian nations have large construction gaps based on current economic conditions, African nations’ construction gaps will dramatically increase in the future as the continent keeps experiencing fast population growth. International volume differences are disproportionately driven by upward construction and by rural areas and small towns instead of cities (including rural upward construction). Lastly, nations/cities with similar levels of economic development may specialize in heights or areas. Overall, the results suggest an important role for land-use regulations and highlight that construction patterns may have significant environmental implications.

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