In tracing more particularly the laws which govern the rise
and fall of rents, the main causes which diminish the expenses of
cultivation, or reduce the cost of the instruments of production,
compared with the price of produce, require to be more
specifically enumerated. The principal of these seem to be four:
first, such an accumulation of capital as will lower the profits
of stock; secondly, such an increase of population as will lower
the wages of labour; thirdly, such agricultural improvements, or
such increase of exertions, as will diminish the number of
labourers necessary to produce a given effect; and fourthly, such
an increase in the price of agricultural produce, from increased
demand, as without nominally lowering the expense of production,
will increase the difference between this expense and the price
of produce.

The operation of the three first causes in lowering the
expenses of cultivation, compared with the price of produce, are
quite obvious; the fourth requires a few further observations.

If a great and continued demand should arise among
surrounding nations for the raw produce of a particular country,
the price of this produce would of course rise considerably; and
the expenses of cultivation, rising only slowly and gradually to
the same proportion, the price of produce might for a long time
keep so much ahead, as to give a prodigious stimulus to
improvement, and encourage the employment of much capital in
bringing fresh land under cultivation, and rendering the old much
more productive.

Nor would the effect be essentially different in a country