US Dollar Index 14-Year Chart

Spec , I don't have data going back 20 years but a cursory glance at 10 years worth of data tends to support the argument ,and although it would be difficult to give a a comprehensive answer as to the precise factors affecting these relationships (ie bn us dollar commodities euro and aussie ) one could hypothesise that their are psychological factors impacting on these so that an increase of demand for commodities in general does impact on euro and aussie demand to the detriment of the dollar and vice versa.

My post immediately below was referring to the "commodities argument " and currency valuations previously alluded to by both spec and Ashraf .

in the early - mid 90s oil was not a good hedge for the dollar and the correlation was not negative throughout. so what makes you so confident that this relationship will not return?

Spec ,regarding your question as to the legitimacy of the secular nature of the dollar,in all seriousness one could write a book on the topic ,but given my lack of time and inclination I'll attempt a brief response. Since around 2000 when prices were at around 120 the dollar has slowly but surely drifted lower and lower .The Highs of 2000 have not been surpassed since. Also ,any rally by the dollar since then has not been able to meaningfully remain above it's 200 day moving average.Clearly then the dollar has been in a serious bearmarket for many years and this is suggestive of very powerful dynamics acting against the dollar which are fundamentally driven and not merely based on sentiment. Consequently one may argue that if the dollar was to reverse its clearly defined downwards path fundamental factors would have to be changing and favouring the dollar . Yet all the evidence seems to be painting a picture where this not the case.With the fed creating dollars out of nowhere and causing an incomprehensible amount of supply relative to demand ,with budget deficits in the trillions and likely to worsen every year,with china massively stockpiling commodities and increasing their gold reserves by huge amounts ,with emerging markets markets entering a new era of growth etc etc it is difficult to argue that the dollar is about to embark on a bullish path for a meaningful amount of time. However given the already mentioned proposition that anything is possible I will change my mind if newer evidence appears on the horizon to augment your arguments. I wouldn't be holding my breath though.