3 ms·

Consider a chart of the recent M2 money supply for the last couple of years: https://fred.stlouisfed.org/graph/?g=16MIK https://fred.stlouisfed.org/graph/?g=16M

by jerf 3y ago

Consider a chart of the recent M2 money supply for the last couple of years: https://fred.stlouisfed.org/graph/?g=16MIK https://fred.stlouisfed.org/graph/?g=16MIK Whether that is "useless" depends on your point. If you want to make a point that they are not large percentage fluctuations you may prefer to anchor it at zero. But if you want to talk about the fluctuations themselves, you want the chart to be full of those fluctuations, not anchored at zero and all the fluctuations just little wiggles relegated to the top. So it does depend on what you want to do, but there are use cases where anchoring at zero is either useless, or even itself at times deceptive, especially in cases where "zero" is not a particularly distinguished value on its own. (e.g., voltage. zero voltage is itself a relative measure to some standard of voltage, so a voltage chart being anchored to zero may not mean anything if zero voltage in some context isn't special but is itself somewhat arbitrary.)

zarzavat 3y ago
If you want to make a chart about the fluctuations themselves, another way would be to show the differences on chart with a centerline at zero and bars that go positive and negative. Or if you really want the cumulative then normalize the first or last data point to be zero. The problem that people have with not starting at zero is how arbitrary it is. You can tell a completely different story depending on where you choose the starting point. So there should be some kind of justification for the chosen Y range.
- jerf 3y ago
  I don't know 100% if you think you're disagreeing with me or not, but I'd consider your second paragraph a restatement of my point from a very different (and still valid) point of view. It's always something that a graph maker should be thinking about for sure, and a blanket "anchor it at zero" is neither desirable, nor even necessarily possible all the time.
tpxl 3y ago
> But if you want to talk about the fluctuations themselves, you want the chart to be full of those fluctuations, not anchored at zero and all the fluctuations just little wiggles relegated to the top. Wouldn't you then plot the _fluctuations_ anchored at 0? Same with voltage, using some 'absolute' voltage value doesn't make sense. If you put ground and zero at 100V and the positive node to 105V, your 5V device will work just fine.

by jerf 3y ago

zarzavat 3y ago

If you want to make a chart about the fluctuations themselves, another way would be to show the differences on chart with a centerline at zero and bars that go positive and negative. Or if you really want the cumulative then normalize the first or last data point to be zero. The problem that people have with not starting at zero is how arbitrary it is. You can tell a completely different story depending on where you choose the starting point. So there should be some kind of justification for the chosen Y range.

jerf 3y ago
I don't know 100% if you think you're disagreeing with me or not, but I'd consider your second paragraph a restatement of my point from a very different (and still valid) point of view. It's always something that a graph maker should be thinking about for sure, and a blanket "anchor it at zero" is neither desirable, nor even necessarily possible all the time.

tpxl 3y ago

> But if you want to talk about the fluctuations themselves, you want the chart to be full of those fluctuations, not anchored at zero and all the fluctuations just little wiggles relegated to the top. Wouldn't you then plot the _fluctuations_ anchored at 0? Same with voltage, using some 'absolute' voltage value doesn't make sense. If you put ground and zero at 100V and the positive node to 105V, your 5V device will work just fine.