Yes there is - but I get what you mean. It's a bit lie 'I go swimming once every 3 days', not 'I go swimming once 3 days'. If you said 'there was one woman to seven men' it kind of makes sense but the implication, or connotation, is not statistical. You might think it's real - there are women and men being put together or something!
In short - you need every! Hope it makes some sense! Tutor Zowee :)