Bizarre employment issue

My nurses say they are graduating 7200 per month. The graph indicates a steady increase in grad rate. Still, the number of unemployed nurses declines monthly without any additional hospitals being built. Country population is increasing though slowly.

The game is most likely turning them into workers. Compare the unemployed graphs for each.
If you look on the Automation page / All logging you'll see when it was done.

Can I stop it?

Not sure, but you can lessen it's frequency.
It seems that you always need an unemployed workers pool to draw from. If you have enough unemployed workers at each level it doesn't happen.
This is not science only what I've noticed. With a reserve around 60k/50k/40k, llw/mlw/hlw, it happens a couple of times a year. When I have less than that it can be monthly.
I have no idea what the exact numbers are or how they are computed. Maybe someone could enlighten us.

I believe if you go to Automation on your first screen and uncheck "Increase employment and move workers to other professions" then it will not do it without you manually choosing to.

Those automation settings stop working at Level 4. This is something the game does in the background. It is more noticeable when you have around 3% unemployment. Government workers, probably due to low salary, seem to be transferred first.
I made a post about it in the Problems section called "Country Automation - GM please respond". You can read Andy's response.

As Marcus said, you can stop the automation if you go to the automation page and turn off the functions.

however, the automation does help while you are learning.
make sure you check education priorities and shortages of workers once automation is stopped.

The automation setting for adjust priority and move workers does not control this..
The info box on the Automation page states that it has no effect past Level 4. In my case I am past L4 and the box was not checked. The log for that feature states nothing was done.
I noticed this when I went over 97% employment.
I was having Hospitals close due to a lack of staff. When I checked daily I would have less Doctors even though their priority was high.
Every game month or two, unemployed Professionals would decrease and common workers would increase.
The game converts Professionals into workers automatically. We have no direct control over it.
On the Automation page, View All Logging, you get the message that some workers have been assigned a different profession.

Andy,

It appears that the game requires a minimum amount of unemployed LL, ML, and HL workers.

Is this really necessary once a player reaches a cert