The disadvantage is lack of flexibility -- you must write a new parser program for each new format, and if a format changes, you must change, recompile, relink, and redeploy the parser program.

Now we want to be more expansive and to hone the design of the program to address chronic poverty and at the same time have the flexibility to respond to shocks when they arise.

A default parameter provides greater flexibility to a program because you can include neither, one, or both of the input parameters when you call the function.