For Franklin D. Roosevelt, who pioneered the concept in 1933, it was 15 – the number of major bills his administration passed through Congress.
For Obama in 2009 it was $787bn – the vast stimulus package he pushed through.
Perhaps you could sum up May’s first 100 days with 17 – the remarkable opinion poll lead her Government is enjoying.
To dismiss the gap between the Conservatives and Labour as all the latter's doing would be remiss.
Yes, we must take this into account, but May has intentionally rolled Conservative tanks even further onto Labour’s hard-earned middle ground, offering a message of social justice, responsible capitalism and competence that has polled well.
But winning over the public in her first 100 days has only been half the battle.
With a majority of only 12 she has been forced to tread the Westminster line carefully – balancing the views of the ‘one nation’ Tories with the increasingly emboldened right wing of her party.
Navigating this delicate landscape has resulted in a number of high-profile climbdowns and conflicting messages.
Contentious plans to extend grammar schools and to force companies to list the number of foreign employees seemed to kick-start Jeremy Corbyn into action, eliciting the rarest of things nowadays – a unified public Labour response.
Both plans were subsequently diluted and May’s team sobered.
The battle between the ‘hard’ and ‘soft’ Brexiteers has been another flashpoint.
May’s decision to immediately appoint Davis, Fox and Johnson to the three ‘Brexit Offices’ was a wise move, yet recent infighting between them, and now with the Chancellor, has caused early headaches.
Given the otherwise strict message control at No.10, this disunity sticks out like a sore thumb. Losing any ground on the communications front would be a disaster for her.
Her managerial approach has proven to be a rather useful weapon so far and polls suggest she is exactly what the public are looking for.
They also suggest her communications operation has been good at reassuring the public that she has the same priorities as them: in September, for example, Britain Thinks reported that May was not just more trusted than Corbyn on reducing immigration and striking new trade deals following Brexit, but on safeguarding the NHS also.
This is a happy place for any Conservative PM to be, at any point during their administration, and particularly one who has taken on so few media opportunities for the public to get to know her as their Prime Minister.
Roosevelt wisely identified the first 100 days as the vital period for any newly elected leader – a relatively short stretch where a certain amount of goodwill is afforded by the public, media and opposition.
May will be acutely aware of the grace given to her so far and will not be celebrating this weekend – partly because that’s not her style.
But partly, too, because she knows more than anyone else that her biggest achievements have not been tangibles like bills, votes or treaties, but simply in keeping control of the agenda and the comms around it, thereby putting 17 extraordinary percentage points between her and the Opposition.
Oliver Foster is managing partner of Pagefield
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