xQuery - Concering Date Decrementation - Yearly

I have been having a problem trying to work out how to display a date decrementing yearly as an xquery. The output I need needs to correspond to a specific .xml file I have. I have my code below which sets the basic format however I cannot understand where I need to place the decrementer in order to set each "Year"

My code is listed below

for $year-pubs in doc("dblp.xml")//year
return <publisher>
       <year-pubs>
            <year>{$year-pubs/author/text()} </year>
       </year-pubs>
  </publisher>



  The expected output .xml output is: 

       <publisher>
          <year-pubs>
               <year>2013</year> 
               <!-- other 2013 records  -->
          </year-pubs>
       <year-pubs>
   <year>2012</year> 
     <!-- other 2012 records -->
</year-pubs>