Balassa–Samuelson effect

By the law of one price, entirely tradable goods cannot vary greatly in price by location (because buyers can source from the lowest cost location). However most services must be delivered locally (e.g. hairdressing), and many manufactured goods such as furniture have high transportation costs (or, conversely, low value-to-weight or low value-to-bulk ratios), which makes deviations from the law of one price (known as purchasing power parity or PPP-deviations) persistent. The Penn effect is that PPP-deviations usually occur in the same direction: where incomes are high, average price levels are typically high.

The simplest model which generates a Balassa–Samuelson effect has two countries, two goods (one tradable, and a country specific nontradable) and one factor of production, labor. For simplicity assume that productivity, as measured by marginal product (in terms of goods produced) of labor, in the nontradable sector is equal between countries and normalized to one.

${\displaystyle MPL_{nt,1}=MPL_{nt,2}=1}$

where "nt" denotes the nontradable sector and 1 and 2 indexes the two countries.

In each country, under the assumption of competition in the labor market the wage ends up being equal to the value of the marginal product, or the sector's price times MPL. (Note that this is not necessary, just sufficient, to produce the Penn effect. What is needed is that wages are at least related to productivity.)

${\displaystyle w_{1}=p_{nt,1}*MPL_{nt,1}=p_{t}*MPL_{t,1}}$

${\displaystyle w_{2}=p_{nt,2}*MPL_{nt,2}=p_{t}*MPL_{t,2}}$

Where the subscript "t" denotes the tradables sector. Note that the lack of a country specific subscript on the price of tradables means that tradable goods prices are equalized between the two countries.

Suppose that country 2 is the more productive, and hence, the wealthier one. This means that

${\displaystyle MPL_{t,1}<MPL_{t,2}}$

which implies that

${\displaystyle p_{nt,1}<p_{nt,2}}$.

So with a same (world) price for tradable goods, the price of nontradable goods will be lower in the less productive country, resulting in an overall lower price level.

A typical discussion of this argument would include the following features:

• Workers in some countries have higher productivity than in others. This is the ultimate source of the income differential. (Also expressed as productivity growth.)
• Certain labour-intensive jobs are less responsive to productivity innovations than others. For instance, a highly skilled Zurich burger flipper is no more productive than his Moscow counterpart (in burger/hour) but these jobs are services which must be performed locally.
• The fixed-productivity sectors are also the ones producing non-transportable goods (for instance haircuts) - this must be the case or the labour intensive work would have been off-shored.
• To equalize local wage levels with the (highly productive) Zurich engineers, Zurich fast food employees must be paid more than Moscow fast food employees, even though the burger production rate per employee is an international constant.
• The CPI is made up of:
  • local goods (which in richer countries are more expensive relative to tradables)
  • Tradables, which have the same price everywhere
• The (real) exchange rate is pegged (by the law of one price) so that tradable goods follow PPP (purchasing power parity). The assumption that PPP holds only for tradable goods is testable.
• Since money exchange rates will vary fully with tradable goods productivity, but average productivity varies to a lesser extent, the (real goods) productivity differential is less than the productivity differential in money terms.
• Productivity becomes income, so the real income varies less than the money income does.
• This is equivalent to saying that the money exchange rate exaggerates the real income, or that the price level is higher in more productive, richer, economies.

The average asking price for a house in a prosperous city can be ten times that of an identical house in a depressed area of the same country. Therefore, the RER-deviation exists independent of what happens to the nominal exchange rate (which is always 1 for areas sharing the same currency). Looking at the price level distribution within a country gives a clearer picture of the effect, because this removes three complicating factors:

1. The econometrics of purchasing power parity (PPP) tests are complicated by nominal exchange rate noise. (This noise would be an econometric problem, even assuming that the exchange rate volatility is a pure error term).
2. There may be some real economy border effects between countries which limit the flow of tradables or people.
3. Monetary effects, and exchange rate movements[note 1] can affect the real economy and complicate the picture, a problem eliminated if comparing regions that use the same currency unit.
4. Taxes are very different in many countries, whereas in a same country taxes are usually equal or similar.

A pint of pub beer is famously more expensive in the south of England than the north, but supermarket beer prices are very similar. This may be treated as anecdotal evidence in favour of the Balassa–Samuelson hypothesis, since supermarket beer is an easily transportable, traded good. (Although pub beer is transportable, the pub itself is not.) The BS-hypothesis explanation for the price differentials is that the 'productivity' of pub employees (in pints served per hour) is more uniform than the 'productivity' (in foreign currency earned per year) of people working in the dominant tradable sector in each region of the country (financial services in the south of England, manufacturing in the north). Although the employees of southern pubs are not significantly more productive than their counterparts in the north, southern pubs must pay wages comparable to those offered by other southern firms in order to keep their staff. This results in southern pubs incurring a higher labour cost per pint served.

In a 2001 International Monetary Fund working paper Macdonald & Ricci accept that relative productivity changes produce PPP-deviations, but argue that this is not confined to tradables versus non-tradable sectors. Quoting the abstract: "an increase in the productivity and competitiveness of the distribution sector with respect to foreign countries leads to an appreciation of the real exchange rate, similarly to what a relative increase in the domestic productivity of tradables does".

Capital inflows (say to the Netherlands) may stimulate currency appreciation through demand for money. As the RER appreciates, the competitiveness of the traded-goods sectors falls (in terms of the international price of traded goods).

In this model, there has been no change in real economy productivities, but money price productivity in traded goods has been exogenously lowered through currency appreciation. Since capital inflow is associated with high-income states (e.g. Monaco) this could explain part of the RER/Income correlation.

Yves Bourdet and Hans Falck have studied the effect of Cape Verde remittances on the traded-goods sector.[2] They find that, as local incomes have risen with a doubling of remittances from abroad, the Cape Verde RER has appreciated 14% (during the 1990s). The export sector of the Cape Verde economy suffered a similar fall in productivity during the same period, which was caused entirely by capital flows and not by the BS-effect.[note 2]

Rudi Dornbusch (1998) and others say that income rises can change the ratio of demand for goods and services (tradable and non-tradable sectors). This is because services tend to be superior goods, which are consumed proportionately more heavily at higher incomes.

A shift in preferences at the microeconomic level, caused by an income effect can change the make-up of the consumer price index to include proportionately more expenditure on services. This alone may shift the consumer price index, and might make the non-trade sector look relatively less productive than it had been when demand was lower; if service quality (rather than quantity) follows diminishing returns to labour input, a general demand for a higher service quality automatically produces a reduction in per-capita productivity.

A typical labour market pattern is that high-GDP countries have a higher ratio of service-sector to traded-goods-sector employment than low-GDP countries. If the traded/non-traded consumption ratio is also correlated with the price level, the Penn effect would still be observed with labour productivity rising equally fast (in identical technologies) between countries.

Lipsey and Swedenborg (1996) show a strong correlation between the barriers to Free trade and the domestic price level. If wealthy countries feel more able to protect their native producers than developing nations (e.g. with tariffs on agricultural imports) we should expect to see a correlation between rising GDP and rising prices (for goods in protected industries - especially food).

This explanation is similar to the BS-effect, since an industry needing protection must be measurably less productive in the world market of the commodity it produces. However, this reasoning is slightly different from the pure BS-hypothesis, because the goods being produced are 'traded-goods', even though protectionist measures mean that they are more expensive on the domestic market than the international market, so they will not be "traded" internationally[note 3]