CBSE conducts the IIT entrance exams – called JEE. There are two levels – JEE(Main) and JEE(Advanced).
The number of aspirants has dropped for the second year in a row by more than 100,000. In the current year, 1.2m students applied for JEE(Main), as against 1.3 m in 2015. The drop in numbers over the years is shown below.
Normally, the top 150,000 aspirants from the JEE(Main) are eligible for JEE (Advanced), who eventually make it to the 10,000 seats available in 16 IITs.
This precipitous drop is probably an indication that many prefer not to now opt for JEE, given that the chances are so low. It could also be an indicator of the fact that there are more options for quality education for aspiring engineers outside of IIT.
Either way, the number of JEE takers seems to have plateaued for some time now.