&gt; Up? At least, that&#x27;s what some of the graphs appear to show.<p>A very slight bias that way, national report shows; since 1971:<p>Lowest tier: +4 percentage points (pp)<p>Lower Middle: n&#x2F;c<p>Middle: -10 pp<p>Upper Middle: n&#x2F;c<p>Highest tier: +5 pp<p>(Difference is rounding errors.)<p>(Incidentally, I <i>really</i> wish there were a way to do the equivalent of an HTML &lt;br&gt; tag in HN comments, without going to code mode.)