Table 2.

Density of networks used in previous experimental assesssments of centrality measures.

Centrality	Network	Number of nodes n	Number of edges m	Density
Group Centrality	Western States Power Grid	4,940	6,594 undirected	0.0005
	Collaborations in astrophysics	16,705	121,251 undirected	0.0008
K-Path	Kazaa file sharing	2,424	13,354 undirected	0.0045
	SciMet citations	2,729	10,416 undirected	0.0027
	Co-authorships in condensed matter	23,133	186,936 undirected	0.0007
	Citations (Cit-HepPh)	34,546	421,578 directed	0.0007
	Company emails at Enron	36,692	367,662 undirected	0.0005
	Social (Epinions1)	75,879	508,837 directed	0.00008
	Social (Slashdot0922)	82,168	948,464 directed	0.00014
Heatmap	University emails in Spain	1,133	5,451 undirected	0.0085
	Hyperlinks in US political blogs	1,222	16,714 undirected	0.0224
	US Airline Flights in 2010	1,572	17,214 undirected	0.0139
	Facebook from UC Irvine students	1,893	13,835 undirected	0.0077
Laplacian	Terrorist network mapped by Krebs	37	170 directed	0.1276
LeaderRank	Users of delicious.com in May 2008	1,675,008	169,378 undirected	0.0000001
Subgraph	Protein–protein interaction (yeast)	2,224	6,608 undirected	0.0026
	Protein–protein interaction (bacterium)	710	1,396 undirected	0.0055
	Words in Roget's Thesaurus of English	994	3,640 undirected	0.0073
	Words in Online Dict. of Library & Info. Science	2,898	16,376 undirected	0.0039
	Collaborations in computational geometry	3,621	9,461 undirected	0.0014
	Citations of papers on graph drawing	249	635 undirected	0.0205
	Internet at the autonomous system (1997)	3,015	5,156 undirected	0.0011
	Internet at the autonomous system (1998)	3,522	6,324 undirected	0.0010
Topological	DBLP research database	664,188	79,128 directed	0.0000001
VoteRank	Friendships of Youtube users	1,134,890	2,987,624 undirected	0.000004
	Co-authorship in condensed matters (arXiv)	23,133	93,497 undirected	0.0003
	Hyperlinks in Berkeley/Stanford webpages	685,230	7,600,595 directed	0.00001
	Hyperlinks in U. Notre Dame webpages	325,729	1,497,134 directed	0.00001

Note that density is calculated as $\frac{m}{n\times (n-1)/2}$ for undirected networks and $\frac{m}{n\times (n-1)}$ for directed networks.