I've observed that "thereby" is mostly followed by (verb+ing) form regardless of whether the sentence takes place in past, future or present. As in this example from the dictionary:
"The number of uninsured cars will rise and the cost to the industry will increase, thereby pushing premiums up further."
However, I seldom see "thereby" followed by a verb in other forms such as past tense. For example:
"This behavior increased demand and thereby pushed prices up still more."
why isn't it "pushing up the prices...". Is either form right,?
I'd be glad if you could give more information/examples on thereby usage