Evaluating latent content within unstructured text: an analytical methodology based on a temporal network of associated topics

Table 2 Characteristics of the temporal network of associated topics

Year	Instances (Number of documents)	Vocabulary (Distinct tokens)	Nodes (Number of topics)	Edges (Topic cooccurrence)
1999	195	15,824	65	468
2000	220	16,927	64	456
2001	211	17,017	60	402
2002	230	17,922	63	420
2003	269	19,323	63	444
2004	303	19,848	58	360
2005	314	20,876	63	393
2006	299	20,704	59	363
2007	401	22,691	65	435
2008	405	22,939	62	435
2009	495	23,975	62	399
2010	509	24,531	65	390
2011	671	25,877	64	408
2012	683	25,897	60	360
2013	793	26,853	61	360
2014	943	27,612	61	339
2015	1019	27,864	62	363
2016	1188	28,262	59	306
2017	1094	28,276	65	372
2018	1229	28,527	63	327

Table 2 lists the characteristics of the temporal network of associated topics, over the 20-year time series. The number of topics (or nodes) listed in Table 2 are those with at least one edge (or cooccurrence) with another topic. Hence, isolated topics not addressed with any of the 70 identified topics are not included in the number of nodes listed in Table 2