Well put Pixy. The US Index is a consistent benchmark designed to measure the US Dollar Strength. EK's "Rolling Average" is simply a baseline that is essentially meaningless and does not cater for long term depreciation.
I suppose the idea was that long term depreciation would be handled through salary reviews but ask anyone who has been here for 10 years if this has been the case and the answer is a resounding and provable - NO.
We must get used to the idea that anything from ERP will evaporate and salaries have been in a consistent decline for years.
Tighten your belts everyone, if you have been getting the full ERP benefit recently, prepare for a cut in your takehome packet.