Right, let’s do this.

Joan Robinson on investment and saving in 10 tweets or less. 1/

By investment is meant an addition to real capital ... This use of the word does not correspond to the everyday sense in which investment means merely acquiring a title to capital. ... Saving is the difference between income and expenditure on consumption. 2/

All incomes are derived either from producing C goods or producing I goods.

All income is spent on C goods or is saved.

The income derived from producing C goods is equal to what is spent on them.

Therefore, what is saved is equal to the income from producing I goods.

S=I 3/

The sum of all the savings, positive and negative, of individuals is the total increase in wealth of the community, and the increase in wealth of the community ... is the investment that has taken place.

But saving is not the same thing as investment. 4/

How does it come about that .. individuals always decide to save just as much as entrepreneurs have decided to invest?

Entrepreneurs decide to expand their plant ... Incomes increase.

With a higher level of income, and the same attitude to saving, the amount saved increases. 5/