Requirements, especially in government, will change quite quickly whatever you do, so I'd argue that fast agile development is more beneficial and cost-effective than slower development cycles.
Can you expand? Can you give an example of requirements changing quickly or frequently in government? Given that they're constrained mostly by budget and legislation I'd argue the opposite.
That notwithstanding, I'd also be very interested to know how agile is a panacea to fast-changing requirements, especially as opposed to techniques such as designing for change (at the architectural level, so not just the implementation level, i.e. loose coupling, encapsulation and abstraction interfaces).
That notwithstanding, I'd also be very interested to know how agile is a panacea to fast-changing requirements, especially as opposed to techniques such as designing for change (at the architectural level, so not just the implementation level, i.e. loose coupling, encapsulation and abstraction interfaces).