If you’re stuck in creating white, european, non-diverse characters and can’t get out of the rut, then try looking at current world statistics for birth rates, such as this handy guide from the CIA or birth rates by map. Or you could check out the Worldometers website, which counts up various stats from today or this year.
If you have a few hours a week spare, check out the free online course The Lottery of Birth from Futurelearn.
For a more personal view, check out THIS talk on writing diverse characters. It’s focussed on the gaming industry, but crosses over to the writing one with very little effort.
The Office for National Statistics can also provide a wealth of information about the current population by theme, so that you can make your own setting as genuine as possible.
For those who write fantasy, fear not! You can take the underlying principles of the above and turn them into questions about your own world (s)- where has the highest birth rates, the lowest crime, which group gets the best education, the best areas for farming or areas most prone to flood? Where are your characters from, and what opinions do they hold about the world around them due to their cultural upbringing?
This can very easily feed into your conflicts and drivers for your characters and provide you with a basis for a story.
What are you waiting for? Go write!