&gt;  Manhattan has twice the people with half the land area, on an island.<p>Manhattan has twice the residents based on U.S. Census population data, but actual daytime population is more than just residents.  A more important statistic is <i>commuter-adjusted population</i> [1], i.e. number of people in an area during normal business hours, including workers.  That&#x27;s where Manhattan and San Francisco really diverge.<p>The commuter-adjusted population of Manhattan is 3.1 M [2], compared to 1.6 M residents [3].  San Francisco has a commuter-adjusted population of 1.0 M [4, 5], compared to 0.8 M residents [5].  In other words, Manhattan&#x27;s population booms almost 200% during normal business hours, while San Francisco&#x27;s increases a modest 25%.  Manhattan may have 2x more residents, but it has 3x more daytime population than San Francisco.<p>Given it has about half the land area, Manhattan&#x27;s daytime population density is thus 6x that of San Francisco.<p>Attitudes on development -- namely transportation infrastructure and building construction -- certainly contribute to that difference.<p>1. <a href="http:&#x2F;&#x2F;www.census.gov&#x2F;hhes&#x2F;commuting&#x2F;data&#x2F;daytimepop.html" rel="nofollow">http:&#x2F;&#x2F;www.census.gov&#x2F;hhes&#x2F;commuting&#x2F;data&#x2F;daytimepop.html</a><p>2. <a href="http:&#x2F;&#x2F;www.citylab.com&#x2F;commute&#x2F;2013&#x2F;05&#x2F;most-important-population-statistic-hardly-ever-gets-talked-about&#x2F;5747&#x2F;" rel="nofollow">http:&#x2F;&#x2F;www.citylab.com&#x2F;commute&#x2F;2013&#x2F;05&#x2F;most-important-popula...</a><p>3. <a href="http:&#x2F;&#x2F;quickfacts.census.gov&#x2F;qfd&#x2F;states&#x2F;36&#x2F;36061.html" rel="nofollow">http:&#x2F;&#x2F;quickfacts.census.gov&#x2F;qfd&#x2F;states&#x2F;36&#x2F;36061.html</a><p>4. <a href="http:&#x2F;&#x2F;ww2.kqed.org&#x2F;lowdown&#x2F;2014&#x2F;01&#x2F;10&#x2F;how-city-populations-change&#x2F;" rel="nofollow">http:&#x2F;&#x2F;ww2.kqed.org&#x2F;lowdown&#x2F;2014&#x2F;01&#x2F;10&#x2F;how-city-populations-...</a><p>5. <a href="http:&#x2F;&#x2F;factfinder.census.gov&#x2F;faces&#x2F;tableservices&#x2F;jsf&#x2F;pages&#x2F;productview.xhtml?src=bkmk" rel="nofollow">http:&#x2F;&#x2F;factfinder.census.gov&#x2F;faces&#x2F;tableservices&#x2F;jsf&#x2F;pages&#x2F;p...</a>