If the measure of a good life is counted in years, the future looks bright, as the average life expectancy in many nations is set to climb.

A recent study has crunched the numbers on 35 industrialised countries from around the globe, and found their future populations will be living longer than today's – in South Korea's case, potentially climbing as high as 90.

Statistically speaking, life expectancy is a measure of how long a newborn can be assumed to live.

Many things can affect this number as individuals face risks posed by diet; lifestyle habits such as smoking or drug use; infant mortality; access to healthcare; and traffic accidents.

A team led by scientists from Imperial College London working with the World Health Organisation ran data from a variety of countries through 21 different forecasting models, using the results to predict the life expectancy of citizens born in the year 2030.

The news is good for most of the countries, with life expectancy continuing to jump in leaps and bounds.

It will come as no surprise to most that women born in 2030 will more than likely live to a slightly older age than men, a trend which appears to be the reversal of how things were before the modern age.

Oddly, we're still not entirely sure why females seem to outlive men across the board, though the study notes numbers seem to indicate the differences between the sexes come down to higher rates of accidents and differences in habits that lead to conditions such as cardiovascular disease.

Researcher Majid Ezzati explained, "Men traditionally had unhealthier lifestyles, and so shorter life expectancies. They smoked and drank more, and had more road traffic accidents and homicides. However as lifestyles become more similar between men and women, so does their longevity."

Women born in South Korea in the next 15 years might want to invest in birthday candles, with a 57 percent chance that their life expectancy will be 90.8 years, breaking the nonagenarian line for the first time in history.

Right now, that number for South Korean women is 85.8, meaning a jump of five years.

French women can also expect a long life of 88.6 years, up from 85.1, followed by Japan at 88.4 years which barely moves from 88.5 years.

South Korean men, on the other hand, can expect a still-respectable 84.1 years in 2030 – the highest predicted for males – up from today's 79.3.

Good news for Australian blokes born in 2030 – they will come in second on the list for men, also expecting to reach 84, just 3.6 years behind Australian women.

This general lift for life expectancy is largely attributed to socioeconomic improvements, better education, improved nutrition among children and adolescents, expanded access to healthcare, as well as factors such as a lower incidence of smoking among women.

While most of the countries studied can expect a significant boost in life expectancy over the next 15 years, the US will see only relatively minor improvements – 82.1 to 83.3 for women born in 2030, and 77.5 to 79.5 for men, putting them on a similar level to life expectancies in Mexico and Croatia.

"Not only does the US have high and rising health inequalities, but also life expectancy has stagnated or even declined in some population subgroups," the researchers write.

Predicting a climb in life expectancy means looking to a future where society will need to care for an ageing population, especially in nations with a declining birth rate.

"The fact that we will continue to live longer means we need to think about strengthening the health and social care systems to support an ageing population with multiple health needs," says Ezzati.

Several decades ago, having a future general life expectancy exceeding the age of 85 was believed to be unlikely.

The researchers themselves point out in their paper an early upper limit of 90 was proposed by some scientists at the beginning of the 20th century.

Should we even be thinking it terms of upper limits?

The current record for the oldest human is held by Jeanne Calment, a French woman who lived to 122 years and 164 days, but it seems unbelievable to think this could ever become a common statistic.

Ezzati doesn't seem to think so. "We repeatedly hear that improvements in human longevity are about to come to an end," he says. "I don't believe we're anywhere near the upper limit of life expectancy – if there even is one."

This research was published in Lancet.