As an example. 

Why Do We Always Seem to Run Into People Abroad?

https://www.thrillist.com/travel/nation/science-behind-chance-encounters-abroad?ueid=b2b86f91d6286348e35a69f5415e6995&utm_source=Sailthru&utm_medium=email&utm_campaign=Thrillist%20Daily-%2011/4/24&utm_term=Thrillist%20Daily 

According to details in this article we can run into a person we know while travelling abroad once in 25 years

 on the average. I did - In Dublin Ireland during the years we travelled abraod almost every year 1961-2007. 

One can make similar estimates if you are probability and mathematically inclined.