earth structures
... that in 2005, about 1.5 billion people lived in earth structures ?
... that in 2005, about 1.5 billion people lived in <b id="mwCUA"><a href="./Earth_structure" id="mwCUE" rel="mw:WikiLink" title="Earth structure">earth structures</a></b> <i id="mwCUI">(example pictured)</i>?