Derek, are you keeping some sort of record, statistics or whatever for your leaflet drops?
It'd be interesting to compare stuff with you from my own small-scale testing I've been doing.
I've put out 5170 leaflets on my own to selected areas so far. I've had 11 leads and turned 7 of those into jobs. Those jobs have given me back £574, so an average job ticket of £82 (crap compared to referrals which is £150-ish).
But.....How's this for an encouraging thought: Every time I push a leaflet through a letterbox it earns me 11 pence

That's made me feel a lot more optimistic about it after doing some areas several times over a few months and not getting a dickie bird.
Of course I haven't taken into account repeat business from the initial job, one of which I've probably done another £500 worth of cleaning for after his initial response to the leaflet. Although it's really difficult quantifying things like that, I'm a bit of an excel junkie so I do keep a lot of stats and figures etc, it's amazing sometimes how different the stats are from what you "think" is the case
