I'M a big fan of charts and graphs. A simple line can tell a powerful story. For instance, if you look at the curve representing Australia's foreign aid budget, you see clearly that your country has turned itself into a global leader in foreign development in the past few years.

In 2009, when the global financial crisis hit, many key aid donors started flatlining their spending.

Australia, on the other hand, started to speed up its already steady rate of increase in foreign aid.

I know the budget has been a big topic of debate in recent weeks.

I am relieved your government decided to keep making progress toward its pledge to invest 0.5 per cent of gross national income on aid.

I hope Australia will reach that target as quickly as possible, and that you'll continue to focus your spending on programs that fight poverty overseas.

I say this because improving the health and productivity of the poorest is one of the best investments you can make in the future of the world and the future of Australia.

Relatively modest investments in development can have a big impact when they're done strategically.

Take the example of the Global Fund to Fight AIDS, Tuberculosis, and Malaria. Created just over a decade ago, the fund pools money from many donors, including Australia, to prevent and treat deadly diseases at an enormous scale and significantly reduced costs.

I recently visited Zambia, where I met Florence Daka, an HIV-positive mother of four. Without the global fund, she would be sick, dying, and desperately searching for someone to take care of her soon-to-be-orphaned, HIV-positive children. Instead, she leads a normal life and her youngest son Stephen was born free of HIV.

There are more than four million people like Florence who would be dead or dying from AIDS if not for the global fund. On top of that, the global fund has detected and treated almost 10 million cases of TB and distributed more than 300 million bed nets to protect children from malaria.

Another great investment your government makes is to an organisation called the GAVI Alliance, which helps poor countries purchase lifesaving vaccines.

Like the global fund, it's only a decade old and has already prevented 5.5 million deaths. What's even more exciting is the potential. GAVI is now working with countries to provide three relatively new vaccines - for rotavirus (the leading cause of diarrhoea); pneumococcus (pneumonia); and HPV, the virus that causes cervical cancer. Together, these diseases killed at least 1.2 million people last year.

The money you invest in GAVI will pay for vaccines we know will save these lives.

One way to measure the global fund's and GAVI's impact is to count the number of people served and the number of lives saved. Another way to measure it is to consider how improved health changes the prospects of a country. Poverty and disease are a vicious cycle. But the global fund's and GAVI's interventions interrupt that cycle. When adults are healthy, they can work. When children are healthy, they can develop fully. Health, productivity, and human potential: these are the basic elements of a thriving society. When poor countries become more prosperous, it's good not just for them but for the world at large and for Australia.

Eighteen of Australia's 20 closest neighbours are developing countries. It's plain to see that your own long-term prosperity and security depend on the progress of development in your region.

Many of your major trading partners, including China, Korea, Malaysia, and Thailand, were once major aid recipients. Today's aid recipients can follow the same trajectory, leading to a brighter future for everyone.

Because Australia is increasingly seen as a leader in development, your investments serve as an example and an inspiration to other donors.

I saw clear evidence of this in 2011, when Australia hosted the game-changing Commonwealth Heads of Government Meeting in Perth.

Prime Minister Gillard and then-foreign minister Rudd pledged $50 million over four years to polio eradication. This commitment catalysed other commitments totalling more than $100 million, helping to restore polio to priority status on the global agenda.

Now, with polio cases at the lowest levels in history (the slope of that curve has been steep and downward, from 350,000 in 1988 to 223 last year), the organisation in charge of eradication activities has released a plan to get rid of the disease by 2018.

I am looking forward to Australia's continued leadership on this issue, which is my personal priority.

Eradicating polio is important for so many reasons. It proves we have the tools, like vaccines, to save lives. It proves that countries around the world have the systems and will to deliver these tools. And it proves that the world can come together to do something extraordinary.

Australia has been an important part not only of the polio story, but also of the larger development success story. These are achievements for which you deserve to feel proud.

Bill Gates is the world's richest man, co-founder of computer giant Microsoft and Co-Chair of the Bill & Melinda Gates Foundation, which he established with his wife to fight third world poverty.