Interesting data has been released by the Council on Tall Buildings and Urban Habitat (CTBUH) which is a non-profit organization on the subject matter. It was found that around 60% of the world’s tallest skyscrapers wouldn’t be in the list if it wasn’t for the space which is un-utilized at the top; something that CTBUH calls ‘vanity height’.

Vanity Height – The Dark Secret Of Tallest SkyScrapers.