Each of the discussion on sovereign wealth funds has focused on their vast wealth – wealth that is so great it has seemed as though these funds could buy the world, if they so desired. But that notion is tested when you realise that Botswana also has a sovereign wealth fund (SWF). Trinidad & Tobago has one too. And Equatorial Guinea. And Timor-Leste.

These are not the sorts of countries that one imagines using their resources to buy up large chunks of Wall Street or the City of London. I'm not expecting to see headlines any time soon revealing that Timor-Leste has just bailed out Citigroup or that Chile is propping up UBS.

The question of what qualifies as a SWF and who has one became important once the International Monetary Fund (IMF) decided to develop a set of "generally agreed principles and practices" to cover how they operate.

This initiative was started after Western politicians and investors got spooked by the sheer, staggering size of some SWFs. The lack of knowledge about the behemoths in the SWF sector – Abu Dhabi, Singapore, Kuwait and Saudi Arabia – has fed conspiracies about their motivation in buying prize Western assets. Are they benign investors or is there an alternate motive designed to forever enrich the Gulf at the expense of London, Paris and New York?

However, the world of SWFs is considerably more varied than many had realised, which makes writing rules to govern their behaviour much tougher. Do we need, for example, to apply the same investment rules to Trinidad's $500 million (Dh1.83bn) Revenue Stabilisation Fund as to the Abu Dhabi Investment Authority (Adia), which has an estimated $700bn in funds? Adia has enough money to buy the entire Western banking system, shut it down and move it to the Middle East; Trinidad has enough money to make the movie of it.

Adia and Trinidad do share the same genesis in that they exist because these countries have gained windfalls from the sale of natural resources. Sudden and vast wealth sounds like my idea of fun but injecting cash straight into a developing economy can cause massive problems such as rampant inflation and an indolent workforce.

In the case of Botswana the surplus wealth ($4.7bn) has been generated by diamonds, specifically its joint venture with De Beers, the diamond miner. Chile's $15bn economic and social stabilisation fund is the result of copper production and Timor-Leste's $1.4bn fund comes from oil.

There are 24 SWFs signed up to the IMF's rule-making process and they include minnows such as Trinidad, the giants from the Gulf as well as developed world funds from Ireland, Alaska and Norway.

It is sensible for them all to be included in the IMF process because you never know who might benefit from the next boom and find themselves with a Qatar-sized fund. Also, the rules may encourage sound and sensible investment practices in funds owned by countries were sound and sensible governments are often in short supply.

However, there is a glaring omission in the SWF list: where are the other government investment vehicles such as Dubai International Capital (DIC) and Mubadala? I realise that there are political and diplomatic reasons why funds such as DIC have not been included within the IMF's remit, but this is a mistake. It is in the interests of SWFs to get these other funds folded into the IMF agenda as attempts to look transparent will be undermined if other government-owned assets are divorced from the process. This is doubly true with funds like DIC and Mubadala, which do have a mandate to be strategic in their investments and are therefore more likely to target potentially controversial assets.

It is also in the interests of non-SWFs to be classed as such because international finance is based on trust and this whole process is about fostering more of that. Greater trust will open more doors to more investment opportunities.

Excluding these government investment funds from rules that cover SWFs is a bad idea but if there is no way around it, a fund like DIC should simply adopt the principles unilaterally. After all, if it looks like a SWF it will be treated like one – even if it is owned by Botswana.

- The writer is a Business Correspondent with The Times of London