>My insight like this goes back to 1978. I was working on coding my first business app for the AP of a home builder. Their manual process involved having a set of ledger cards for each house they were building. Each card represented one cost center. There was a cover card for each house where they put the total of the individual cards. At the end of each month, they'd go through each set, doing the totaling. The business was growing and it was taking 10 to 15 days each month to do the totals, even though many of the houses were complete and had no new costs and some hadn't been begun yet and had no costs.
>
>I said they should put a rubber band around the cards for a house after they'd totaled it. The first time there was a new item posted for a house in the new month, take the rubber band off. Then, at the end of the month, they only needed to total the cards for houses with no rubber band. That took it back to being something they could do on the first business day of each month.
>
>It's amazing how obvious this seems after I've typed it, but they were too close to the process to see it. They'd always totaled every set of cards every month.

IOW, http://ndragan.com/pv/brush_too_far.html