The Rating changes after each closed Task and only Tasks completed for the past 6 months are taken into account. The Rating depends on the Task price and the result. If the Buyer has confirmed Task results and paid for the Task, your Rating increases. If you failed, the Task has been sent to Disputes and it was solved in the Buyer's favor, your Rating will be decreased. As a result, the higher the Task price is and the more Tasks you complete successfully, the higher your Rating is.