BBC London's Errol Murray looks at how they do it.

One million people go to the Toronto International Carnival or Caribana every year.

The Caribbean-style street festival not only generates a lot of fun but it makes around �120m for the city.

Toronto's Deputy Mayor Case Ootes told BBC London that "it has a tremendous impact" on the multi-cultural city.

We have to make sure we are giving back

Sherene Shaw, Toronto City Councillor

All the bars are full and all the city's 13,000 hotel rooms are booked up for the event.

Denzil Minan-Wong, from the Toronto Economic Development Committee, said that every person attending there spends an average of $600.

"More than 20% of that $600 is spent on accommodation," he said.

"They spend 17% spent on food and beverages and 28% is spent on shopping."

Businesses benefit

Just a fraction of what is made at the Toronto event would cover the �5m it costs to police Notting Hill Carnival.

One-and-a-half million people attend the two-day London street party, but as soon as it finishes they are gone.

Mr Minan-Wong's advice is, "try and keep them in London longer".

"If you can understand why they are coming and what their habits are, then you can start to build on that to create more economic benefit for the Notting Hill community and for the City of London."

Toronto businesses benefit from the carnival, but as in London, the event itself still needs a measure of financial support.

Sherene Shaw, a city Councillor in Toronto, said: "Because of the nature of carnival it may be difficult to generate the kinds of funds needed so we have to make sure we are giving back."