Supercharger is absolutely correct. You cannot possibly put a number on the opportunity cost arising from a diploma holder.
The diploma holder has many opportunites to continue to upgrade in terms of education wise and with that 'paper', he/she will be able to open more doors and opportunities out there.
And with a little bit of luck and with the right attitude, there really isn't a cap on his/her pay as his/her career progresses along. ie: the sky is pretty much the limit here.
Where as the 2 job holder, will reach a cap sooner or later and probably max out at S$4k. Of course there are exceptions and successful businessmen without education, but then again, there are a lot of more failures and people regretting not having proper formal education as well.
A non-educated KTV owner may be very successful. But I am sure, if a Harvard MBA graduate should open a KTV, he would be even more successful because of his expereince and knowledge, he will know how to grow his business and find ways to draw in the high net worth clients out there through his networking. He may also be able to draw in corporations as well.
There are always 2 sides to a coin, but one should always consider choosing the side where education comes first and upgrading and chasing that 'paper' as a necessity. It does sound crap , but the paper is how the world and society grades us and how much we draw each month (starting pay) stems from there.
Just my thoughts.
