Read the following extract from the 2015 Preliminary annual report of Seek Ltd.

Critical accounting policies
The preparation of financial statements requires the use of certain critical accounting estimates. It also requires management to exercise its judgement in the process of applying the Group’s accounting policies. The areas involving a higher degree of judgement or complexity, or areas where assumptions and estimates are significant to the financial statements, are disclosed in the relevant notes.

Required
Locate the most recent annual report for Seek Ltd and identify the accounting areas that management believe have the greatest potential impact on its consolidated financial statements due to its associated assumptions and estimations. Select one area and explain the significant judgement and estimation involved in measuring the item for balance sheet purposes.