source: http://f2017cpsc683.ucalgaryblogs.ca/wp-admin/post-new.php

In this visualization, it is not possible to identify the different counties. However, main point of the authors is to convey that age of first child birth has been increased between 1995 to 2015. So, this simple graph properly display the age distribution of the mothers in all the countries for two time period. I like that this graph is not overly complicated by adding label for counties.