The MACH-IV test of machivellianism (Christie & Geis, 1970) on this website has been used to collect data. This page summarises the correlations between MACH-IV scores and demographic characteristics as well as other statistical information about the test. The data used here is available for download at the open data page.
The graph below shows average scores by age.
Sample sizes get a little bit low for the higher ages (n=~20 for age 70) so there is some noise on the right hand side of the graph, but the trend is pretty clear. Machiavellianism decreases with age.
The graph below shows the distributions of scores by gender.
It can be seen that men score higher than women on average, and at the high end men are 5 times as likely to get the highest possible result (~1% versus ~0.2%). This fits with the general stereotype of women being nicer than men. Calculated as a effect size, men scores 0.58 standard deviations higher which is normally interperted as a "medium sized effect" (see Thresholds for Interpreting Effect Sizes).
The graph of average scores by race is below.
Race differences were small.
Differences for sexual orientation are below.
There does not appear to be any clear trend.