A problem is that people have different things in mind when they ask for estimates. For some, an accurate estimate would mean that 50% of the time you're over

A problem is that people have different things in mind when they ask for estimates. For some, an accurate estimate would mean that 50% of the time you're over and 50% of the time you're under. But management too often takes this type of 50/50 estimate and then makes all kinds of promises and contracts based on it. If you want an estimate that we're going to hit 99% of the time, that is going to be much much higher. Many places I've worked management would balk at any discussion of percentages like this when making estimates. As the saying goes: What you say is "there's a 50% chance we'll be done in 6 months, if there's no distractions". What they hear is "I promise we'll be done in 6 months".