Since 2001 the dollar has been in steady decline. Against the £ the dollar has fallen from a low of £1 = $1.45 to close to the £1 = $2 mark. Against the Euro the $ has also depreciated from 0.85 to the present level of 1 Euro to $1.35.
From several perspectives the fall in the value of the dollar appears to be following basic economic fundamentals and whilst these imbalance continue the dollar may continue to fall.
Firstly the US current account deficit is remaining at record levels. The exact amount of debt with the rest of the world is predicted to be around $710 billion for 2006 
Basically this means America is importing more than it is exporting, causing an outflow of money. In recent years this huge level of debt has been bought by countries like Asia who have been happy to buy into the dollar for its perceived status as a “stable and secure” currency. However there is increasing evidence Asian bankers are no longer so confident in the American economy. Thus they are seeking to divest from the dollar and reduce their dollar holdings. As this occurs the dollar will have to fall as there is insufficient buyers of American debt.
Secondly the future for economic growth is no longer looking so positive. Growth forecasts have recently been downgraded. The OECD has downgraded is growth forecasts for the US economy from 3.6% to 2.4%. Pessimists such as Nouriel Roubini, of Roubini Global Economics  are predicting a recession in the US by the middle of 2007. An important factor in declining growth forecasts is the falling US consumer confidence.
Related to this is a signal that the previous ebullient housing market may have at last turned the corner. Whilst new house prices continue to rise. The median price of old houses have fallen by 3.5% since last year. Whilst a fall of 3.5% may not sound that much, it is the biggest on record. Also rising house prices have been a key factor in maintaining consumer spending in recent years. The level of personal debt amongst US consumers is at another all time high. The ratio of consumer debt to disposable income has risen from 62% in 1980 to 127% in 2005 
Thus a fall in house prices will have a powerful knock on effect on the rest of the US economy as consumers struggle to meet levels of mortgage and other debt. Falling house prices could leave American consumers with negative equity. (A mortgage bigger than value of the house) This is very likely to lead to falling spending. Another consequence of this high level of consumer debt is that the US economy will be particularly sensitive to any rise in interest rates. Higher interest rates would be one solution to a falling currency and may be necessary to attract investors to finance America’s trade deficit. Although the prospect of the Fed raising interest rates is remote at the moment. Continued falls in American dollars would cause a rise in the long term interest rates on American secutities.
However some economists argue that prospects for the dollar may not be as bad as some predict. Firstly as Anatole Kaletsky argues  in an era of globalisation and deregulated financial markets, trade deficits are not as difficult to finance as they used to be. Empirical evidence suggests that trade deficits are very unreliable as a guide to exchange rate movements. Firstly one of the few countries with a current account surplus is Japan. Their current account surplus has been growing and yet the Yen is one of the few currencies to have fallen against the dollar. 
Secondly although American growth is slowing at the moment it is not doing much worse than the EU and Japan economies. The gap in interest rates between the 2 economic areas is still only about 2%. If there are good reasons for the dollars weakness there are less good reasons for the strength of the EURO. Also some American economists such as Ben Bernanke of the Federal reserve remain optimistic about the state of the US economy arguing growth is only marginally below trend rate.
However it is important not to underestimate the importance of general market sentiment regarding the American economy. Political problems such as in Iraq have to an extent undermined America’s standing as a leader of the World in both an economic and political sense. For 50 years America has been the undisputed global economic superpower, but slowly perceptions are changing that the era of the dollar may becoming to an end. As people switch out of dollars it could create a powerful multiplier effect as investment bankers are reluctant to hold onto their dollar assets.
America to a large extent can’t avoid a period of adjustment as it seeks to deal with its triple deficits, trade deficits with the rest of the world, consumer debt, and US government debt. Whether the period of adjustment is gradual or painful will depend upon 2 things. Firstly how significant will be the fall in US house prices and consequent fall in consumer confidence. Secondly it will depend on the attitude of Asian bankers, in particular the Chinese. Since they hold so many $ assets they may try to manage a gradual devaluation, a continuation of the past 5 years. However if the dollar does lose its status as the reserve currency of the world, there could be a growing stampede as America’s creditors seek to cash in their cheques. This would exacerbate the fall of the dollar, causing real economic hardship for America and the rest of the world.
The only thing for sure is that European consumers are likely to be get some real bargains from shopping in America for the considerable future.
 Household debt Bubble at Monthly review see also: http://www.federalreserve.gov/releases/Z1/Current/ (March 9, 2006)
 Demise of Dollar greatly exaggerated – Anatole Kaletsky