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What governs the shape of price history graphs?
I agree with @Turukawa that the x-axes need to be the same to make a direct comparison.  However, the graphs you linked make me think of introductory calculus:  If you time averaged plots, speculative investments (gold, housing) seem to have many large concave up time periods and the dow jones has many concave down sections.  Using the concavity test: If the first derivative tells you about the rate of change, the second derivative tells you about the rate of change of rate of change.  Remember back to Physics 101:  1st derivative is velocity & second derivative is acceleration.   It would be interesting to have the same time scales for your plots & compare these accelerations between the two.  I suspect the more volatile investments would have larger (in magnitude) accelerations during boom/bust cycles than less speculative investments.