When considering the plight of 153 million children, even a small percentage of children that could be adopted results in large absolute numbers. If only 1% of orphans worldwide were able to be adopted, this would result in 1.53 million adoptions every year; even just one-tenth of 1% of orphans would result in 153,000 international adoptions annually.
Source: Adoption Advocate No. 57: Reconsidering Intercountry Adoption: Who wants to Adopt and Who Could Be Adopted? Published March 2013 by Christopher Balding. Read more.