Because if NGDP were growing at a stable rate then the log of NGDP would be a perfectly straight line.

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The last time I saw him, he said with a perfectly straight face that as long as he owned the place the first Enos Grahame could come back whenever he liked and find the whole house just as he remembered it!

NPR: Excerpt: The Sherwood Ring

Time after time my mind has been blown by the ease in which Ponting gets off the mark with a perfectly executed straight or on-drive down the ground.

BBC: Justin Langer column

First-rate gay authors such as Alan Hollingshurst continue to write about gay protagonists, but fewer gay people seem to feel driven to read them, even as more straight readers feel perfectly comfortable doing so.

FORBES: Just What Is 'Gay Culture' In 2013?

Set the flat end on a perfectly flat surface, and a bubble of air points straight up.

FORBES

That miss was immediately matched by Pandev, with the Macedonia ace shooting straight at the onrushing Gordon rather than squaring for Stojkov, who was perfectly placed to convert.

BBC: Scotland 2-0 Macedonia