Simulations of the new design suggest that number will increase to 86 percent in 2021, increasing the chances of close racing from 2021 onwards.
In a dramatic overhaul revealed in Austin, the American owners of the commercial rights, Liberty Media, introduced budget caps, a new auto and rules created to develop closer and more environmentally-friendly racing.
The Brit has won the US Grand Prix six times in his career, with five of those victories coming at the Texas track.
Formula 1 has finally unveiled the new direction in which the sport will head beginning the 2021 season. However, it excludes marketing costs, the salaries of drivers, and of the top three personnel at any team.
"But even the vehicle that has been developed with CFD and the wind tunnel [by F1] has got a respectable amount of performance and it has been developed by essentially a relatively small number of aerodynamicists and hours in a wind tunnel compared to a normal team". Budgets have been escalating. "F1 is nearly a victim of its own success".
"They've been pretty well thought out, but they will need development, like any regulation".
The extension will see F1 races continue to air live and commercial-free on either ESPN, ESPN2 or ABC, while all practice sessions, qualifying and races will air live and in replay across ESPN platforms, including on-demand replays on the ESPN App. ESPN will continue its partnership with United Kingdom broadcaster Sky Sports to bring its presentation of F1 to American viewers. Previous efforts at spending limits have been "gentlemen's agreements" that have been largely ignored, Brawn said.
"We've tried for these in the past and we've not been successful", he said.
"But, well, there's not many gentlemen in the paddock I'm afraid and so that was a failure".
Expanding the season could strain those budgets.
That figure is fixed for 21 races, with $1m to be added for any races above that total. Vietnam has been added as a race in 2020 and F1 is now making plans to add a Miami Grand Prix in 2021.
The sport will stick with the existing V6 turbo hybrid engines introduced in 2014 after abandoning plans to change them.
In principal, the 2021 F1 cars will have a radical new design philosophy and striking new look with sweeping bodywork, simplified front wings, bigger rear wings, increased underbody aerodynamics, wheel wake control devices, simplified suspension and low-profile tyres with 18-inch rims. Teams will also be forced to put inexperienced drivers behind the wheels of their cars in a minimum of two practice sessions each season, which may result in more shake-ups to the established driver hierarchies, and this approach may benefit teams that can't now rely on calling drivers up from other series in which they participate.
Hamilton will be sure to claim his third straight Formula One world title on Sunday unless Mercedes team-mate Valtteri Bottas wins the race. This team has shown they are better prepared and in best position to react to changes. "Sometime next year, my mindset will to switch into 2021 and wanting to be a pioneer in that era", Hamilton said.
I don't particularly see myself going anywhere else. "I love being part of Mercedes". I love being a part of the brand.
Racing Point's Lance Stroll and and Alfa Romeo's Antonio Giovinazzi completed the top 10. "But there's no reward for that".