The percentage increase in your salary will decrease over time
The percentage increase in salary by gaining one more additional year of experience, decreases as the total number of experience stacks up.
Example
The salary of a guy who has 1 year of experience to when he gets 3 years of experience will be significantly high because he has spent 200% additional time in gaining experience from that field.
But at the same time the salary of someone who has 10 years of experience to 12 years of experience will not be that high because he has only spent 20% additional time in gaining experience on top of whatever he had already.
Closing
That being said this is ofcourse a very linear way of thinking about salary hike with only a single variable of {time} factored into it. There are so many other components that might contribute to your growth in career