[51] The Joint Stock banks have published monthly returns since January 1921. Excluding the half-yearly statement when a little “window-dressing” is temporarily arranged, the extreme range of fluctuation has been between 11·0 per cent and 11·9 per cent in the proportion of “cash” to deposits, and between 41·1 per cent and 50·1 per cent in the proportion of advances to deposits. These figures cover two and a half years of widely varying conditions. The “proportions” of individual banks differ amongst themselves, and the above is an average result, the steadiness of which is strengthened by the fact that each big bank is pretty steadfast in its own policy. In order to follow, therefore, the train of causation a stage further, we must consider what determines the volume of their “cash.” Its amount can only be altered in one or other of three ways: (_a_) by the public requiring more or fewer notes in circulation, (_b_) by the Treasury borrowing more or less from the Currency Note Reserve, and (_c_) by the Bank of England increasing or diminishing its assets.[52] [52] For the aggregate of its liabilities in the shape of deposits and of notes in circulation automatically depends on the volume of its assets. To complete the argument, one further factor, not yet mentioned, must be introduced, namely (_d_) the proportion of the banks’ second-line reserve in the shape of their holdings of Treasury Bills, which can be regarded as cash at one remove. In determining what is a safe proportion of “cash,” they pay some regard to the amount of Treasury Bills which they hold, since by reducing this holding they can immediately increase their “cash” and compel the Treasury to borrow more either from the Currency Note Reserve or from the Bank of England. The ninefold proportion referred to above presumes a certain minimum holding of Treasury Bills, and might have to be modified if a sufficient volume of such Bills was not available. This factor (_d_) is, however, also important because the banks in their turn are open to pressure by the Treasury, whenever it draws to itself the resources of their depositors--whether by taxation or by offering them attractive longer-dated loans--and uses them to pay off, if not Ways and Means advances from the Bank of England (which reduces the banks’ first-line reserve of cash), then alternatively Treasury Bills held by the banks themselves (which reduces their second-line reserve of bills).