W2 question post I-140 Approval

[debut2005]

My H1B Wage is            : 65000 

My EB3 Labor wage was : 71000

according to my salary iam getting the below

1) 2012 : 71000

2) 2013 : 76800 ( Based on my salary 6400 X 12) + 5000 ( bonus) = 81800

3) 2014 : 76800 ( Based on my salary 6400 X 12) + 3000 ( bonus) = 79800 (Projected)

 

I have this question over here that is it possible to have a lower wage due to less bonus because someone told me that once your company runs a higher wage , they cannot pay you less for the subsequent years as long as you are in the same company.