Brooks's law: why adding people makes a late project later

Your software project is late, so your boss adds four people, and it ships later still. Fred Brooks saw it happen on one of the biggest software projects of the 1960s, and in 1975 he wrote it down as a law. Here is why it works that way: the myth of the person-month, work that cannot be split, onboarding new developers, communication overhead and integration. Then the moves that do work when the deadline will not move.