Every preventive measure in normal individuals implies a certain amount of self-restraint, and in proportion as prudential motives are strong is the self-imposed restraint easy and effective.
The existence of these two qualities, prudence and self-control, is a very important factor in human character, and upon their presence and prevalence in its units depend the progress and stability of society.
But the birth-rate varies in an inverse ratio with these qualities.

In those communities or sections of communities, where these qualities are conspicuous, will the birth-rate be correspondingly low.
There is another class of people that has strong desires to keep free from the cares and expense of a large family.

These are, too, good citizens and belong to good stock.

They are those possessed of ambition to rise socially, politically, or financially, and they are a numerous body in New Zealand.
They are quite able to support and educate a fairly large family, but as children are hindrances, and increase the anxieties, the responsibilities and the expense, they must be limited to one or two.
There is still another class that consists of the purely selfish and luxurious members of society, who find children a bother, who have to sacrifice some of the pleasures of life in order to rear them.
Now all those who prevent have some rational ground for prevention, and at least are possessed of sufficient self-control to give effect to their wish.

They include the best citizens and the best stock, and from them would issue, if the reproductive faculty were unrestrained, the best progeny.
One grave aspect of this limitation is that, as a rule, the family is limited after the first one or two are born.