A country slightly bigger than Texas is projected to match the US population by 2050 — and it shows how radically the world is changing

• According to new estimates, Nigeria is expected to nearly double its population in the next 27 years.
• Nigeria's stunning growth is also indicative of the growth of the African continent.
• The rise is in contrast to a growing number of countries that will experience population declines.

It was recently World Population Day.

The annual United Nations designation is not only a chance to recognize "the dreams of all 8 billion of us on our planet," as UN Secretary-General António Guterres put it in a blog post on Tuesday, it's also a chance to take stock at just how rapidly the world around us is shifting.