• from https://msdn.microsoft.com/en-us/library/ms189035(v=sql.120).aspx

    you can use the following command to shrink both the data and log of a db to include 10% free space for growth:

    DBCC SHRINKDATABASE (UserDB, 10);

    But I was thinking, why do you want to shrink the db, as over the period of next year it will again need to expand to store new data ... 
    Disk space is cheap ...

    You can also of course consider running the job monthly instead of annually, in case you can easily identify which records to archive and purge.