Itinerant voyagers of the global investment scene no doubt know about Citigroup, labelled here and there as the world's biggest bank. Aficionados will also recall one of the almighty bank's many golden eras, including the one under Charles Prince, who quit as CEO and chairman in November last year, in the wake of the imploding, and then exploding, US subprime crisis. 

Today, Wall Street's banks are in disarray, and while the scars from the earthquakes and twisters in credit markets are yet to really start healing, the sector has decisively lost any leadership it ever had in investment markets. In the past few weeks, the global capitalisation of the broader financial services sector has been overtaken by the broader resources group, now worth more than $6 trillion.

Beyond the wild games that Wall Street bankers like to play - varying the form but hardly the underlying content - the world is well into an era of fundamental structural change. Measured in today's money terms, the value of raw materials has been falling since 1800, about as far back as anyone has been able to measure. There have been blips in the long term downtrend, most noticeably when Japan industralised after the Second World War.

This time around the leading drivers are China, India, Brazil and Russia, at the front end of an industralising emerging world. Even now, six years into the new commodities supercycle (if that's what it is), the value of raw materials has a long, long way still to rise before reverting to anywhere near even the mean (average) level of the past 208 years. After decades of low prices, consumers are increasingly confronted by the rarity value of raw materials. 

The smart money in investment markets is already well into this theme, and seeking new sub-themes, switching and rotating from one sub-sector to another. The most recent example, on a near-epic scale, has been seen in potash, an impure form of potassium carbonate (K2CO3), mined, often at great depth, from deposits left behind by evaporated prehistoric seas.

To compare apples with apples, take three stocks listed on the New York Stock Exchange: Citigroup (which may or may not still be the world's biggest bank; it may still matter), PotashCorp (based in Canada), and Mosaic, based in the US. 

PotashCorp and Mosaic both mine potash, and also phosphates; both also mine nitrogen from the air we breath, using natural gas running through huge plants. Eventually, refined, malleable products are packaged into various combinations of fertiliser - NKP (usable forms of nitrogen, potassium and phosphorus).

Today, Citigroup's stock price is 44% lower than five years ago. Compare that with Mosaic, with a stock price appreciation of 1 200% over five years, and, for PotashCorp, an appreciation of 1 300% over five years. If that were not enough, Citigroup's market value today is a rather modest $120bn, roughly equal to the value of a combined Mosaic and PotashCorp. 

A decade ago, and less, resources companies - and their downstream relatives such as steelmakers - were reviled and loathed as the last prehistoric smokestack industries, sure to die horrible deaths as dot.coms overwhelmed the world. When Wall Street had its head badly kicked on that story, and then took a further beating after the bankruptcy of Enron in late 2001, it stumbled around like a creature of prime importance until subprime stuck its lovely head out.

The next time Wall Street investment bank Goldman Sachs takes yet another position in commodity markets - where it is widely acknowledged as one of the world's biggest players - it may want to look over its shoulder at the likes of PotashCorp.  Goldman Sachs has a market value of $70bn, compared to PotashCorp's $60bn. Strange, but true, and going forward, guaranteed to become weird.