This book was not quite what I expected as it focused entirely on economics. He first spends a few chapters presenting evidence that the fertility rates really are declining, not just in Europe and America, but around the world. (This book is a few years old; I think the fears of "overpopulation" are fading, though I know there are some who still believe them.) Then he launches into chapters of statistics showing how decreasing population is a bad thing for any country's economy and why nothing except an increase in fertility can really solve the problem. (Other options, for example, would be working to an older age, increases in productivity, innovations, etc.) There were lots of interesting statistics, many of which supported other things Kansas Dad and I have read about the medical system, for example. (See this review.)
According to Mr. Longman, the main reason people are not having more children is economic - they don't feel like they can afford to give children everything they are supposed to have, including a college education. (They also wait longer, building up their financial status, and then encounter fertility problems, a corollary of the main reason.) So in the final few chapters, he presents some ideas for encouraging an increase in the numbers of children parents have, all economic.
I don't necessarily disagree with all of his ideas for promoting families and family life, but I think taking a purely economic view is wrong. Some people have fewer children than they desire because they are worried about being able to feed them or house them. Many more people are having fewer children because they are worried about being able to pay for their college education or give them cars when they turn 16 or pay for childcare and private preschools. Giving more money to the family will not address those fears.
Instead, our culture needs to change our view of what's necessary for a happy, healthy childhood and start in life. Of course, a change in culture is exactly what Mr. Longman wants to avoid. Though he doesn't address any chapters to the dangers of those who are having more children, he mentions a few times the "fundamentalists" (which he defines in the Preface as "all who rely on literal belief in ancient myth and legend, whether religious or not, to oppose modern libreral and commercial values") who continue to have more children than everyone else. (I therefore began the book a little trepidatious of what I would encounter, as I am most certainly one of the "Catholic fundamentalists" he mentions.)
If no alternative solution can be found, our future will belong to those who reject markets, reject learning, reject modernity, and reject freedom. This will be the fundamentalist moment.
So his whole goal is to provide financial incentives to people who would otherwise not have children so our culture does not eventually grow and change as a greater percentage of the population comes from large families, those that may (just for example) view the arrival of a new child as a blessing from God to be cherished and loved, even if we cannot afford his or her college education.
In the end, I'm not sure financial incentives would work at a national level. I have reservations about incentives in general and financial ones in particular. I guess I'm hoping for a cultural change.