How to measure a project's progress? If time is your metric, then the last 20% should be done in 20% of the total time. (And that's right, when the OP says she was 80% done, she actually was 50% done.)
If your metric is something else, what could it be? And perhaps it is not the best metric after all: a loading progress bar that goes quickly to 80% and then slows down (by a factor of 4) until the end may not be the best progress bar after all.
I guess that the difficulty is to get a precise idea of the time you need to finish something.
The metric given to the client is that of time, but the metric that ends up being measured is (for lack of a better term) "visible product completion", i.e. percentage of product that 'looks' completed. If I read OP right, the last 20% that is being talked about in the article is mostly a nip here and a tuck. The overall product, from this point onwards, almost always remains largely constant.
To bring in yet another analogy, think of the project as a car being refurbished. The last 20% of work may not change much in terms of external chassis, but it is all about fine-tuning the engine, and the drivetrain. The client still sees the same car that you showed him at "80% done," except now the engine runs much better and the car purrs like a sexy, sexy kitten.
The problem, IMHO, is you can't give an accurate metric no matter how much you try.
If you give a liberal estimate and end up doing 80% of the product in 50% of the time, the client will expect you to finish the 20% in 12.5% of the original time-frame - the very 20 % that almost always takes about 80% of time. On the other hand, if you take 80% of the estimated time-frame to deliver 80% of the product, the remaining 20% will always trip you up because it almost always needs another 80% of time.
I've found that the best way to keep everyone happy is to finish 80% of the product in 50% of the time but show the client 50% of the product and spend the remaining 50% of time, finishing the 20%. It's a win-win, IMHO.
>I've found that the best way to keep everyone happy is to finish 80% of the product in 50% of the time but show the client 50% of the product and spend the remaining 50% of time, finishing the 20%. It's a win-win, IMHO.
That is a very clever approach. I don't think I've ever heard of that before. I'll have to give it a try.
Time is a great metric, but the total is only known when you're done. Before that, you need other metrics that you can compare to your estimates, if you want to be able to correct.