Paco Underhill is an environmental psychologist and the founder and CEO of research firm Envirosell. He is also an accomplished writer and speaker.

Paco Underhill penned Why We Buy: The Science of Shopping, said to be the biggest-selling retail book of all time. Published in 1999, it has been released in 27 languages. He also wrote 2004’s Call of the Mall: The Geography of Shopping. He has written columns and other articles for various publications, including the New York Times, Wall Street Journal, and Money Magazine.

Writing aside, Underhill has his hands full with speaking engagements. In 2008 alone, he traveled to 19 countries, where he spoke to various professional groups and trade associations. He also regularly talks on BBC Radio and NPR.

With Envirosell, he empowers banks, stores, manufacturers, and other commercial entities with consumer behavior research. By taking factors like the human body and gender into context, the company helps companies grow more familiar with their market. In fact, Envirosell tests prototype stores around the planet.

Founded in 1979 as Environmental Analysis & Planning Consultants, Envirosell is headquartered in New York City, with offices in Milan and Sydney. Envirosell clients have included Microsoft, McDonald’s, Coca-Cola, Unilever, adidas, Hewlett Packard, Kraft, Estee Lauder, and Nokia.

Paco Underhill worked with land management firm, Project for Public Space, in 1975. He then taught environmental psychology at the City University of New York from 1977 through 1978. He later sat as the only non-Japanese member of the advisors’ board at ad agency Hakuhodo.