# Topology of the World Tourism Web
## 3 Results and Discussion
### Network Topology and Structure
#### 3.1.3 Centrality Measures  
Different centrality measures shed a different light on a node's importance in the network; nonetheless, their interpretation must be adapted to the properties of the examined network (meaning that the classical interpretation in some cases cannot be applied due to the nature of the observed phenomenon). Countries' rankings by centrality measures are reported in Table 11.  
Closeness centrality is the highest (>0.9) for the United States (0.97), followed by Canada, the United Kingdom, France, and Germany. The values are normalized to enable comparison. The lowest value of closeness centrality exists for the island countries and dependent territories. The closeness centrality calculation is based on the sum of the shortest paths between a node and all other nodes. The sum is the denominator, so a higher sum leads to a lower closeness centrality measure, indicating the node's worse position in the network. This is true for the island countries and dependent territories, as they reveal a few direct connections. However, this may also occur due to reporting issues (namely its thoroughness--if the countries do not report arrivals from all countries but only from most prominent emitting markets, such measures may occur). Closeness centrality indicates that the United States is both well connected and has well-connected neighbors. The countries with normalized closeness centrality values close to 1 tend to have many first-degree connections, which establishes their central position in the network. According to the harmonic closeness centrality, which accounts for data asymmetry, there are 11 countries with values above 0.9 (besides those already mentioned, there are Italy, Switzerland, the Netherlands, Australia, and Belgium). Stated countries are best connected (directly and indirectly), but from the tourism network perspective/ that does not necessarily mean that they are the most important in the network or that the shortest paths are actually going to be used. Rather, their connectedness makes them interesting from the information dissemination and cultural exchange perspectives. Eigenvector centrality shifts the focus from a country's own connections to its neighbors' connections, meaning that some connections are more valuable than others. Eigenvector centrality shows the following ranks: Canada (1), Belgium, Ecuador, the UAE, and Finland (0.995). Given the rank, it seems that Canada is most connected to other high-degree nodes. For comparison, in 2014, countries ranked by eigenvector centrality were China (0.694), Hong Kong, Macao, Korea, and Taiwan; and most of these countriesprevailed on top ranks by eigenvector centrality since 2002 [8]. While some differences may arise from the used data, the other part is probably a result of global tourism trends. The calculated values for 2018 are significantly higher, and 43 countries have an eigenvector centrality over 0.9. This can be interpreted in combination with changes in the network density [7] as a general increase in connectivity in the tourism network. The authority and hub measures are calculated by the HITS algorithm [59], primarily devised for web page analysis. The analysis distinguishes hubs that compile links to authoritative sources and authoritative sources of information. In a way, hubs are a stop on the way to an authoritative source, while an authoritative source is observed as the destination. This property would better explain tourist movements over different target countries within a single trip. Nevertheless, in the context of this network, hubs can be perceived as best-connected countries to other important countries in the network. In a way, they serve as bridges, not in general terms--only to the authoritative nodes. Accordingly, authoritative nodes are most important countries that receive guests from hubs. This means that guests from hubs support the top tourism status of the authoritative countries, while hubs thrive due to tourists from other countries (with smaller authority and hub measures).