How does the organization of congress lend itself to pork-barrel legislation?

Governments have long used the power to tax and spend to favor certain constituencies with special benefits over and above what a system based on a formula or need would provide. In a democracy, elected officials generally have well-defined, geographic-specific electoral bases, so such benefits tend to be location-specific and highly visible, usually taking the form of infrastructure spending on such projects as courthouses, highways, airports, and government office buildings.