Wealth inequality might increase. The United States has a grave problem with excessive wealth being concentrated in the hands of the few. In this year's State of the Union Address, President Obama reported that the wealthiest 1% own 40% of the wealth in he United States, and the bottom 80% own only 7% of America's wealth.
If people live to be 125, the wealth inequality problem would probably increase very significantly. The main reason is that death is a major factor that helps to limit wealth inequality. When very rich people die, the government gets a large share through inheritance taxes, and usually the person's fortune is divided up among several people. If the very rich are living to the age of 125, that end-of-life wealth redistribution is delayed for several decades.
Unemployment might increase. In many fields it is very hard for young people to find a job, partially because of all of the older people holding on to their jobs. If people live to be 125, people might hold on to their jobs until they are 90 or 100. One can only imagine how negative an effect that might have on the unemployment rate.
Ideas might stagnate. It has been said many times that some inappropriate or weakly supported theories never die until their advocates finally grow old and die. This problem of conceptual stagnation might became worse if people have 125-year lifespans. One can imagine people saying things such as this: “I've been advocating string theory at this university for the past 90 years, and I'm sure not going to change my mind now.”
Retirement programs might bankrupt. A program such as Social Security was designed under the assumption that people would typically die around the age of 70 or 75. What happens when people start living to be 125? It might be enough to send many a retirement program into bankruptcy.
Overpopulation might get worse. The world's population was 6 billion in 1999, but grew to 7 billion in 2011. It is predicted to grow to 7.7 billion by 2020. By the time we develop science for 125-year lifespans, the world might be groaning under a terrible overpopulation crisis (exacerbated by global warming and resource depletion). Much longer lifespans may make the problem significantly worse. The extent of this difficulty will depend on how expensive lifespan extension is. If scientists develop a fairly inexpensive youth pill, and billions start living beyond the age of 100, this might make overpopulation much worse. But if life extension depends on very expensive techniques that only the rich can afford (as depicted in the visual below), the effect on overpopulation might be fairly small.
An ad of the future
Dementia might proliferate. Longer lifespans might be produced by the introduction of some general technique or medicine that slows aging in all parts of the body. But it is just as likely that longer lifespans will be produced through techniques that allow people to replace or rejuvenate particular parts of the body. In the latter case, there will be a very great risk that people will get younger hearts, younger livers, younger lungs, and younger arteries before they get younger brains.
The reason for this risk is that the brain is much more complicated than any other organ in the body. Compared to the brain, the heart and the lungs and the liver are ridiculously simple (and might well be produced by sophisticated 3D printers). So probably decades before there is anything like a technique for rejuvenating the brain (or stopping the aging in the brain), there will be techniques for replacing the heart or the lungs or the liver.
Why is this a problem? It's because people will be tempted to make organ replacements that give them much longer lifespans, but leave them with the same old brains, brains that will tend to become demented when people reach an age of 85, 90, or 95 (because of Alzheimer's disease, strokes, and normal brain aging).
One can only imagine what a cruel twist of fate this might end up being. An 80-year-old might have an operation giving him a new heart, followed by an operation giving him new lungs. He might then rejoice after being told he can look forward to forty more years of life. But then five or ten years later, he might become demented and senile. His extra decades might be spent in a state of vacant senility in a nursing home, at tremendous cost to society.
So you may be saying: no problem; before getting a new heart or lungs, I'll just ask my doctor whether he's sure this won't end up being an expensive ticket to a decade or two in a nursing home. But it's as likely as not that if you ask your doctor, “Are you sure I won't get senile when I'm 100 or 110?” he will simply say: “I don't know.”
So people now about 50 or 60 may be faced with a very tough choice in a few decades. You may be told that some fancy high-tech operation may give you 30 years of additional life, with the risk that you may be spending half of that time as a senile, demented person in a nursing home. Which choice will you make?
Let us hope that they come up with huge breakthroughs in preventing dementia and strokes, medical science that you will be able to afford, so that you will never face such a choice.