There's a theme I've been pounding on for years that, IMHO, developer productivity is actually going down rather than up over the years. I used to make comparisons in developer productivity between command-line interfaces (CLI) and graphical user interfaces (GUI).
My point has been that developers were focused on functionality in the CLI world because of limited presentation options. Therefore, one would spend maybe 10-20% of the project designing the interface and the rest of the time with functionality and reporting.
With the advent of Windows 3, we're GUI and now had a whole bunch more things to plan that had nothing to do with the actual functionality of the application...such as what fonts to use, precision control placement, modal versus non-modal dialogs, etc. So, perhaps, we're looking at 50% interface and 50% functionality.
Now with a lot of business applications exclusively using web interfaces, we have a third area of concern in application development: systems integration: Network issues, request handlers, security, etc. Plus, web UI is not quite as flexible as Windows UI so we spend even more time working out the user interface. I figure that now we spend 30% on integration, 40% on interface, and 30% on functionality.
And, so.....let's do the math but establish a truism first.
GUIs, be they web or desktop, do not generally enhance specific business functionality; they enhance user productivity. For example, being able to look at 5 different chart-of-accounts entries, each in it's own spiffy non-modal window, does nothing to aid the process of closing a period nor does it force multiply the developers time to implement the closing code.
So, the rule here appears to be that GUI applications do not shorten the development time to create business-oriented functions. And, arguably, web applications increase the amount of time required to implement the user interface because of the lesser flexibility of web controls over desktop controls.
My example above is typical of a simple accounting application. Let's look at what the CLI development effort might well be:
UI design and coding: 20% = 20 hours
Functional design and coding: 80% = 80 hours
TOTAL 100 hours
Now let's look at a desktop GUI application. Bear in mind that our UI efforts are 50% of the time now, however, there's nothing in a GUI versus CLI that makes functionality; i.e., closing a fiscal year, any easier. I'm reversing the order of the tasks to highlight this:
Functional design and coding: 80 hours (50%)
UI design and coding: 80 hours (50%)
TOTAL 160 hours
The cost to implement the GUI solution is 60% higher for the developer with little or no increase in business productivity.
With the web app, the numbers go to:
Functional design and coding: 80 hours (30%)
UI design and coding: 96 hours (40%)
Systems integration: 80 hours (30%)
TOTAL 254 hours
The web application is two-and-a-half times more expensive with little of no functional gain. Scary thought, isn't it.