zeb187
Is your question "How can commercial banks increase their assets?". Or do you want to know how central banks and commercial banks work in lock step to increase the money supply?
My understanding on "How can commercial banks increase their assets?" is this. First of all commercial banks can effectively create assets themselves by gaining deposits and then lending out a multiple of what they have received in deposits. This is fractional reserve banking. So, if a bank receives $1,000,000 in deposits and decides to keep a 10% reserve, it would hold $1,000,000 and lend out $9,000,000. This $9m are new assets for the bank, created out of nothing. That is why banks compete so fiercely for deposits.
Historically, and I mean going back to Greek and Roman times, this has been regarded as an illegal practice. Why? Because two people believe they have the immediate use of the same money: the depositor believes he has full and immediate access to the $1m, and the person receiving the $9m loan believes he has full access to those monies. Money cannot be in two places at one time. (However, if someone loaned the bank $1m and the bank lent out the $1m at a higher rate of interest, this would be legitimate entrepreneural activity.)
Banks have always been tempted to lend out monies on deposit and have done so secretly, knowing it to be misappropriation of funds. In Spain in the middle ages, bankers were publicly executed for this fractional reserve banking. Also, historically, banks have not been able to carry this practice out in the long run because as soon as word got out, there would be a run on the bank and it would fail. And this is an example where one could not insure against bank failure because of the moral hazard involved.
To explain how commercial and central banks work in lock step to increase the money supply this is my understanding. To make fractional reserve banking work governments are needed, first to legalise a fraudulent activity and second to provide a central bank to act a lender of last resort. The big beneficiaries of this were the banks themselves for whom this is a very profitable process and governments who greatly benefit from the increased ability to borrow.
When a government wants to create money they do not do anything as crude as printing more notes. The central bank writes a cheque on itself. It has nothing to back this up, of course, but governments have given central banks the power to do this. The central bank then goes into the open market and purchases something. It could be anything, but normally it is their own debt, government bonds. The people who have sold the assets to the central bank then deposit their cheques with a commercial bank. Hey presto, new money has been created! The commercial banks then places their cheques on the central bank.
The government has now created something out of thin air, but it is this ability to create money out of nothing plus the multiplier effect of fractional reserve banking that turns this into a truely awesome process of credit expansion.
As soon as the commercial banks have received the cheques from whomever the government has purchased assets, the capital base of the banks is increased. The commercial banks can now lend out against this capital base on the assumption that not everyone will want their money at the same time. This is fractional reserve banking. Let us say that the banks require a capital base of 2%. This means that the banks can then lend out 50 times the money that the government had created out of nothing initially.
So, that is my understanding as to how the banks create money; and it is banks in the plural: commercial banks and central banks.
On the process of credit expansion I recommend Murray Rothbard's "The case against the Fed". And on the historical distinction between deposits for safekeeping and deposits for loans I recommend Jesus Huerta de Soto's "Money, Bank Credit and Economic Cycles".