Parkinson's law of triviality, also known as "bikeshedding", argues that organizations give disproportionate weight to trivial issues because they are easy to understand. For example, if a proposed solar power plant includes plans for an employee bike shed, then there will be a lots of debate about the bike shed while the complicated engineering issues are overlooked.
According to some of the data on this page - https://en.wikipedia.org/wiki/Slavery_in_the_United_States - in around 1860, about 12.5% of the population of the US were slaves.
So I'm not really sure why fact 166 is framed the way it is. Of course, it's still terrible, and maybe I'm missing the point?
Here's a YouTube video about child labour in India which is actually kind of slavery but we don't realise that
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