Kent can look up actual crashes to plot the so-called crash pulse (the shape of a car's deceleration curve) and the places where a body made contact with the vehicle.
And while the United States knew of plans of an attack, John Brennan, Obama's top homeland security and counterterrorism adviser said they had failed to uncover the actual Christmas Day plot.
They are what you get when you plot data for poor and rich countries together at a given moment in time, but actual levels of various pollutants in any individual country plotted over time wiggle around a lot more.