An estimated total global audience of 800 million tuned in to watch Michael Schumacher win his seventh F1 title this year.
This was a 6% increase on last year's cumulative season audience, but with the addition of two new grand prix in 2004 - in Bahrain and China - the average audience per race actually fell by 6%.
While the Bahrain Grand Prix attracted 55 million viewers, making it the second most popular of the season, the China race held in Shanghai was the second least popular with an audience of 32 million.
The UK-based marketing communication and media agency, Initiative, which has tracked F1 viewing throughout the season, puts this down to the large time difference between China and Europe, which contains 75% of F1's global audience.
The China Grand Prix kicked off in the early hours of a Sunday morning in core European markets; the Bahrain race was the usual Sunday afternoon affair.
According to Initiative, the challenge for F1 is how to increase its global appeal without losing audiences in its established markets such as Europe and South America, which have a long motor racing heritage, and thereby increasing F1's effectiveness for sponsors and advertisers.
Initiative stresses the importance of the "hero factor" in motor racing, using the examples of the successes of the drivers Fernando Alonso, Zsolt Baumgartner and Takuma Soto on the marked increase on F1 viewership in their home countries - Spain, Hungary and Japan respectively.
Spain now has the fifth-largest F1 audience globally, after Alonso finished fourth in the 2004 Drivers' Championship as part of the Renault team.
The presence of a local hero brings in marginal viewers who are rooting for their man, whether he consistently gets on the podium or not, getting them more engaged in the sport and leading them to share their F1 experiences and extend the F1 brand in the process.
Initiative believes F1 has the potential to be the world's most popular annual TV event.
By Martin Hemming