So, I decided to take a look at two questions.
1. Is there a decline in the number of manufacturers?
2. If that happened, when?
Of course, this brings about a third question. Have been oscillations in that number? Why?
I took the Wikipedia list of manufacturers. Yes, there it is a column: starting year and ending (sigh!) year. Now, Ciro, copy and paste to Excel. Ready. Darn, extract two columns with starting and ending year... a while. Create a grid with the years marked, that was easy. Sum every column, easier. Calculate number of manufacturers every year. Check.
Now, graph.

Discuss.