One side of the problem is covered in the answers and comments already given.

The other side - I would argue the biggest side - is that women not only live longer, but that they now usually work and earn money. Marriage is no longer the only respectable profession a woman can take. So there is much less pressure on them to a) marry early, and b) marry at all. A century ago, an unmarried 30 year old woman was a failure, just like an unemployed man of the same age. This no longer holds.

Besides that, the increase of life expectancy is due a decrease in infant mortality, rather than in teenage or young adult mortality. This means that not only the pressure for early marriage is lesser, but also the pressure for early motherhood. A century and a half ago, you could not expect having two or three children reaching adult age without giving birth to half a dozen or more. And the reproductive age span of women is relatively short; a 30 year old woman has already gone over half of it, and consequently can be expected to bear only half the children a 15 year could.

One side of the problem is covered in the answers and comments already given.

The other side - I would argue the biggest side - is that women not only live longer, but that they now usually work and earn money. Marriage is no longer the only respectable profession a woman can take. So there is much less pressure on them to a) marry early, and b) marry at all. A century ago, an unmarried 30 year old woman was a failure, just like an unemployed man of the same age. This no longer holds.

Besides that, the increase of life expectancy is due a decrease in infant mortality, rather than in teenage or young adult mortality. This means that not only the pressure for early marriage is lesser, but also the pressure for early motherhood. A century and a half ago, you could not expect having two or three children reaching adult age without giving birth to half a dozen or more. And the reproductive age span of women is relatively short; a woman aged of 30 has already gone over half of it, and consequently can be expected to bear only half the children a woman at the age of 15 could.

One side of the problem is covered in the answers and comments already given.

The other side - I would argue the biggest side - is that women not only live longer, but that they now usually work and earn money. Marriage is no longer the only legitimate profession a woman can take. So there is much less pressure on them to a) marry early, and b) marry at all. A century ago, an unmarried 30 year old woman was a failure, just like an unemployed man of the same age. This no longer holds.

Besides that, the increase of life expectancy is due a decrease in infant mortality, rather than in teenage or young adult mortality. This means that not only the pressure for early marriage is lesser, but also the pressure for early motherhood. A century and a half ago, you could not expect having two or three children reaching adult age without giving birth to half a dozen or more. And the reproductive age span of women is relatively short; a 30 year old woman has already gone over half of it, and consequently can be expected to bear only half the children a 15 year could.

One side of the problem is covered in the answers and comments already given.

The other side - I would argue the biggest side - is that women not only live longer, but that they now usually work and earn money. Marriage is no longer the only respectable profession a woman can take. So there is much less pressure on them to a) marry early, and b) marry at all. A century ago, an unmarried 30 year old woman was a failure, just like an unemployed man of the same age. This no longer holds.

Besides that, the increase of life expectancy is due a decrease in infant mortality, rather than in teenage or young adult mortality. This means that not only the pressure for early marriage is lesser, but also the pressure for early motherhood. A century and a half ago, you could not expect having two or three children reaching adult age without giving birth to half a dozen or more. And the reproductive age span of women is relatively short; a 30 year old woman has already gone over half of it, and consequently can be expected to bear only half the children a 15 year could.