Let’s look further into Shiduch Island. The 100 boys graduate High School and 10 go to work or college and 90 go to Yeshivah.
The 100 girls graduate High School and 10 go to work or college and 90 go to Seminary.
3 years later, of the 90 boys 30 want to learn in Kollel, 30 want to be learner earner(intending to be a Ben torah) and 30 will be frum, but not really be “into learning”.
3 years later of these 90 girls,80 want to marry a ben torah, but only 60 boys qualify for that criteria. 10 might marry a boy like that hoping she can change him but that leaves some more girls out(actually a higher percentage than the age problem). Also a large percentage of these girls want to marry the Kollel boys or the higher echelon learner-earner (emphasis on the learner part).
That my friends is the essence of the Shiduch Crisis.