Ventana software support forum

Dear Forum members,

I'm currently working on my first System Dynamics project. I'm trying, among other things, to model the process of recruitment of teachers (let's say in a university).
Im my model, there are 4 grades for teachers (Assistants, assistant professors, associate professors and professors). I defined a target students/teacher ratio so as to simulate the total number to recruit each year.
Now I'm facing the problem of the repartition of this number between the four grades. This repartition (of recruitment) should be done so a defined repartition of the levels of teacher grades should be reached.
For example: 0.5 of the teachers are assistants, 0.3 of the teachers are assistant professors, 0.15 of the teachers are associate professors and 0.05 are professors.
I defined 4 variables indicating the proportion of the recruitment of each grade but I still don't know how to formulate their equations.
looking for your help. I'm sorry for the quality of my English

[Edited on 7-4-2008 by Rania]

You should first set up an aging chain - see the molecules. New hires come in as assistants, progress to assistant professors, then associate professors the full professors. Betweeen each stage people will drop out. After this is done you can add the hires into later stages if it still seems necessary for your purpose.