Huge sums have been raised to fund this year's US presidential election campaigns. But where does Mitt Romney's and Barack Obama's funding come from?

Election campaigning in the United States is big business. The latest figures from the Federal Election Commission show that the Barack Obama campaign has raised over $900m so far, while Mitt Romney's team raised more than $800m in the same period - and that does not include the hundreds of millions of dollars raised by other independent groups.

But where does the money come from? This year's election is the first since 1972 that is completely privately financed, after both candidates opted for private, leaving no limits on how much they can raise.

The vast SuperPACs also have a huge role to play, since they were conceived by the supreme court's citizens united ruling in 2010, which allows outside groups to raise funds to campaign for or against a candidate. These groups are independent from the candidate - and are controversial because donors not obliged to disclose their identity - but they allow vast sums to be raised by individual donors, or groups of individuals/employees.

Most of this money is spent on aggressive attack ads which, according to the Center for Responsive Politics, have made campaigns much more unpredictable, as the candidates themselves have little control over these ads.

The graphic shows where in the country, and from which organisations, each candidate's donations are coming from. It also shows that Obama is soaring ahead in terms of small individual donations, such as those that helped get him smash previous fundraising records in 2008. But whether the huge sums amassed by the two campaigns will make a significant difference to their campaign, has yet to be seen.