I am trying to isolate a simple model for GDP accounting in the one person economy also known as the Crusoe economy. Because Crusoe lives alone and has dominion (exclusive control) over all items of economic value I assume he assigns zero value for rent as the return on land and extraction of raw materials. This means income is attributed to wages and profit. Also I assume Crusoe invests only in capital and holds zero inventory in the firm or business sector of his economy. He counts all other output as transfers to consumption in the household sector.

In terms of economic value instead of prices I want to know if wages and profit have a mathematical description in terms of respective contributions to total output?

- Identity for Gross Domestic Product

Output = Income = Expenditure

- Classical factors of production

land, labor, and capital

- Classical factor payments

rent, wages, and profit

- Income in the circular flow assuming zero rent

income = wages + profit

- Expenditure in the circular flow assuming zero inventory

expenditure = capital + consumption

- Robinson Crusoe GDP identity with simplifying assumptions:

output = capital + consumption = wages + profit

Questions:

Is there a non-price equation for wages in terms of output and profit?

Is there a non-price equation for profit in terms of output and wages?

Do these identities hold?

wages = consumption?

profit = capital?

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1 Answer

I will only answer the last question because without further qualification the first two questions do not seem to make sense (see the my comment). Also to make everything cleaner I will use $w$ for wages, $\pi$ for profits, $Y$ for output, $C$ for consumption and $I$ for capital spending.

Do these identities hold?

$$w= C \\ \pi = I$$

No. There is nothing in your system above that would suggest the above should hold. As you remarked on by definition:

$$\pi +w = Y = C+ I \implies \pi + w =C + I$$

Given the above the profits are actually equal:

$$\pi = C + I -w \text{ or } \pi = Y -w $$

and wages are equal to

$$w = C + I – \pi \text{ or } w = Y – \pi $$

The reason why the two identities ($w=C$ and $\pi =I$) won’t hold might be best visualized by some practical example. Let us assume some overtly simplistic production function where $Y = L + K$, here marginal product of labor and capital are both $1$ so wage *per* unit of labor will be $1$ and return on capital also $1$.

Now, I am not sure if this was your question about ‘prices’ but note we do not need to necessarily need to use some real world currencies here and this prices could be denoted in apples, bananas etc (as commonly done in theoretical models – especially in international economics – see Feenstra Advanced international trade for some examples) but I will leave the units vague for simplicity. In addition note that GDP as a statistical measure – not as a concept of output – just look at production sold at market so that would in Robinson Crusoe economy be zero because there are no market transactions – but I assume here you are interested in the underlaying concept of output rather than statistical measure.

The above out of the way, let us assume that Robinson Crusoe starts 10 units of labor that he gets every time period, that he can invest in capital goods which cost exactly 1 unit of output and let see some example of $Y$ calculation across 2 different periods.

Period 1: Since there is no capital here output is produced with labor, as discussed above the price of labor is 1 so when 10 units of labor are supplied we get that $w=1(10)=10$, So we have $Y=w+\pi = Y=10+0$, now this by definition has to be equal to all spending but there is no reason why we should assume spending on consumption has to be equal to 10. That is one possibility but any combination of $C+I=10$ would work here. Let us assume that $C=5$ and $I =5$.

Period 2: By our assumption that it costs $1$ to acquire $1K$ now the Crusoe has $10L, 5K$. Given that the profit (under which you decided to put returns on capital) are given by $\pi = (1)5$, and wages are $w=(1)10$ so now output is equal to $Y= 5+10 =15$. As previously consumption and investment has to be equal $15$ *together* but there are various ways how you can achieve that. $C$ could be 5, which would mean $I=10$ or $C=15$ which would mean $I=0$, as long as $C + I =15$ any value for $C$ or $I$ that satisfies the equality will work.

Hence, generally $w\neq C, \pi \neq I$ save for special cases where $C$ and $I$ are choose by Robinson Crusoe to be exactly equal that amount.