Nobody knows and it isn't really important. If you have been a member for two years and have over 200 hubs, your guess is as good as anyone's. If hub writers really knew what the 'system' was, the score could be manipulated.
You might try adding some photos, graphics or videos to your hubs and see if there is any difference. For instance if you are talking about drawing a diagram-- you might show an example of a diagram to enhance your point.
Do your best, keep improving your hubs, and be happy.
Can anyone know that by which factors hubpage writings are scored. I don't see any stable score of each page. The score is fluctuated very frequently. One of my hubpage is:http://hubpages.com/hub/OSI-Reference-M...