By Charlotte Denny

For half the world's population the brutal reality is this: you'd be better off as a cow. The average European cow receives $2.20 (Â£1.40) a day from the taxpayer in subsidies and other aid. Meanwhile, 2.8 billion people in developing countries around the world live on less than $2 a day.

The facts of global inequality are truly staggering. The richest 25 million Americans have an income equal to that of almost 2 billion people, while the assets of the world's three richest men, even after the recent fall in the value of stock markets, is greater than the combined income of the world's least developed countries.

Or consider this: the living standards of Sierra Leone, ranked bottom of the United Nations' human development index, are roughly equivalent to those in the west 600 years ago. Average income per head stands at only $130 a year - less than the $1-a-day level that the World Bank regards as subsistence level.

The impact of such extreme poverty is devastating. The average Sierre Leonian can expect to live until age 37, a life expectancy level not witnessed in the west since the industrial revolution. Three in every 10 children die before their fifth birthday in Sierra Leone, while infant mortality rates are higher than in England in 1820.

Two centuries ago, income per head in Britain, the world's richest country at the time, was three times higher than that of Africa, then the planet's poorest region. Today, the world's richest country, Switzerland, enjoys per capita income nearly 80 times higher than the world's poorest region, south Asia.

One World Bank economist has warned that as television and cinema bring home to the poor the gap between their lives and the west, the rich may have to lock themselves in gated enclaves to keep out the dispossessed and angry masses.

Grinding poverty is propelling migration, driving the best and brightest from the developing world to seek better opportunities elsewhere. Borders in the west are being sealed to economic migrants, with the result that the trafficking of people has become a more lucrative trade than drug smuggling.

Two years ago at the UN millennium summit, world leaders set themselves the task of halving global poverty over the next 15 years. They promised to eradicate hunger, reduce under-five mortality by two-thirds and get every child of primary school age into a classroom.

The cost of meeting these goals is estimated at between $40bn and $60bn on top of current aid spending - about a sixth of what the west currently spends on subsidising its farmers.

In its most recent assessment of the progress towards the goals set at the summit, the UN warned that 33 countries, totalling a quarter of the world's population, are likely to miss half these targets. Most such countries are in Africa. If living standards in the poorest states continue to rise at the current snail's pace, the UN estimates that it will take 130 years to rid the world of hunger.

Extraordinary efforts will be needed to get sub-Saharan Africa back on track, the UN says. Even to achieve just the target of halving poverty would require growth of almost 4% in income per head over the next 15 years, a heroic task for many sub-Saharan countries where living standards are now lower than they were 30 years ago.

But the task, while difficult, is not impossible. The proportion of the world's poor living in absolute poverty has fallen from 24% in 1990 to 20% today, because of rapid growth in east Asia.

In 1960, Senegal and South Korea had a GDP per head of $230. By 2000, South Korea had a per capita GDP of $8,910, even after the setback of the Asian economic crisis. Living standards in Senegal, however, had barely improved, with GDP per head at $260.

Fifty years ago, South Korea's main export was human hair; today it is a hi-tech leader supplying components for America's computer industry. Massive state support for the silicon chip industry in the 1970s gave the country a competitive edge which paid dividends in the 1980s and 1990s when chips became the building blocks of the hi-tech revolution.

Africa faces a hard task following Asia's success. Blighted by debt, conflict and unfavourable geography, it faces an unequal struggle in the current world system. Moreover, while South Korea was allowed to protect its infant industries from being overwhelmed by more mature competitors, Africa is being required to open up its markets by the International Monetary Fund and the World Bank.

The chances of Senegal following in South Korea's footsteps seem increasingly slender as rich countries continue to pull the development ladder up behind them.

But as globalisation leads to greater interdependence, tackling poverty is becoming a political as well as a moral imperative. A more just world would also be a more stable one.