In the long run inflation is generally believed to be a monetary phenomenon while in the short and medium term it is influenced by the relative elasticity of wages, prices and interest rates. The question of whether the short-term effects last long enough to be important is the central topic of debate between monetarist and Keynesian schools. In monetarism prices and wages adjust quickly enough to make other factors merely marginal behavior on a general trendline. In the Keynesian view, prices and wages adjust at different rates, and these differences have enough effects on real output to be "long term" in the view of people in an economy.

A great deal of economic literature concerns the question of what causes inflation and what effect it has. A small amount of inflation is generally viewed as having a positive effect on the economy.

One reason for this is that it is difficult to renegotiate some prices, and particularly wages, downwards, so that with generally increasing prices it is easier for relative prices to adjust. Many prices are "sticky downward" and tend to creep upward, so that efforts to attain a zero inflation rate (a constant price level) punish other sectors with falling prices, profits, and employment. Efforts to attain complete price stability can also lead to deflation, which is generally viewed as a negative by Keynesians because of the downward adjustments in wages and output that are associated with it.

More generally because modest inflation means that the price of given good is likely to increase over time there is an inherent advantage to making purchases sooner than later. This effect tends to keep an economy active in the short term by encouraging spending and borrowing, and in the long term by encouraging investments.

High inflation, though, tends to reduce long-term capital formation by hurting the incentive to save, and to effectively reduce long-term spending by making products less affordable. Deflation, by contrast, leads to an incentive to save more and encourages less short term spending potentially slowing economic growth.

Inflation is also viewed as a hidden risk pressure that provides an incentive for those with savings to invest them, rather than have the purchasing power of those savings erode through inflation. In investing, inflation risks often cause investors to take on more systematic risk, in order to gain returns that will stay ahead of expected inflation. Inflation is also used as an index for cost of living adjustments and as a peg for some bonds. In effect, inflation is the rate at which previous economic transactions are discounted economically.

Inflation also gives central banks room to maneuver, since their primary tool for controlling the money supply and velocity of money is by setting the lowest interest rate in an economy - the discount rate at which banks can borrow from the central bank. Since borrowing at negative interest is generally ineffective, a positive inflation rate gives central bankers "ammunition", as it is sometimes called, to stimulate the economy.

However, in general, inflation rates above the nominal amounts required to give monetary freedom, and investing incentive, are regarded as negative, particularly because in current economic theory, inflation begets further inflationary expectations.

Increasing uncertainty may discourage investment and saving.

Redistribution

It will redistribute income from those on fixed incomes, such as pensioners, and shifts it to those who draw a variable income, for example from wages and profits which may keep pace with inflation.

Similarly it will redistribute wealth from those who lend a fixed amount of money to those who borrow. For example, where the government is a net debtor, as is usually the case, it will reduce this debt redistributing money towards the government. Thus inflation is sometimes viewed as similar to a hidden tax.

International trade: If the rate of inflation is higher than that abroad, a fixed exchange rate will be undermined through a weakening balance of trade.

Shoe leather costs: Because the value of cash is eroded by inflation, people will tend to hold less cash during times of inflation. This imposes real costs, for example in more frequent trips to the bank. (The term is a humorous reference to the cost of replacing shoe leather worn out when walking to the bank.)

Menu costs: Firms must change their prices more frequently, which imposes costs, for example with restaurants having to reprint menus.

Relative Price Distortions: Firms do not generally synchronize adjustment in prices. If there is higher inflation, firms that do not adjust their prices will have much lower prices relative to firms that do adjust them. This will distort economic decisions, since relative prices will not be reflecting relative scarcity of different goods.

Hyperinflation: if inflation gets totally out of control (in the upward direction), it can grossly interfere with the normal workings of the economy, hurting its ability to supply.

Bracket Creep (also called fiscal drag) is related to the inflation tax. By allowing inflation to move upwards, certain sticky aspects of the tax code are met by more and more people. Commonly income tax brackets, where the next dollar of income is taxed at a higher rate than previous dollars. Governments that allow inflation to "bump" people over these thresholds are, in effect, allowing a tax increase because the same real purchasing power is being taxed at a higher rate.

As noted, some economists see moderate inflation as a benefit; some business executives see mild inflation as "greasing the wheels of commerce." A very few economists have advocated reducing inflation to zero as a monetary policy goal - particularly in the late 1990s at the end of a long disinflationary period, when the policy seemed within reach.