If those subway ads are more effective against the cautious Martins than against the reckless Maxwells, then they are a threat to the hapless Joans.
Previous ads have been more effective against the Maxwells than against the Martins.
mnli hypothesis: Previous ads have been more effective against the Maxwells than against the Martins. premise: If those subway ads are more effective against the cautious Martins than against the reckless Maxwells, then they are a threat to the hapless Joans.