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(Hirschman, 1964) and the Gini concentration index
(Gini, 1912). The HHI index, widely used in
literature, measures the degree of competition in the
market. Considering an industry with N firms it is
possible to measure the market share of each firm,
HHI is calculated by adding the square of the market
shares of each firm as:
N
HHI = Σ S
i
2
i=1
(2)
where S
i
are the market share of each firm measured
in percentage terms. For example, in the case of a
market formed by four firms with shares
respectively of 30%, 30%, 20%, 20%, HHI is equal
to 2600 (30
2
+ 30
2
+ 20
2
+ 20
2
). The index is
structured in a way that it increases both when the
number of firms in the industry decreases and when
the gap between firm size widens. An HHI index
lower than 1000 indicates a market that is close to a
competitive context. The markets in which HHI
ranges from 1000 to 1800 are usually considered
moderately concentrated. If HHI is greater than
1800, the degree of monopoly power becomes more
significant.. The HHI index, calculated for
Registrars at national level at the end of 2010,
resulted in Italy 1,389.92. The index, compared with
data of 2005, resulted increased, because both the
number of Registrar decreased and the number of
registered domains increased. Therefore it is not
possible to talk about monopoly, and moreover the
number of firms at national level proves to be high
(1,842 Registrars). The Gini concentration index,
unlike HHI, is a standard index, which ranges from 0
to 1. The Gini index is equal to 1 in case of
maximum concentration (this happens when, for
example, considering income distribution in a
country, only one individual earns the entire amount
of income), while it is 0 in a situation of even
distribution (all individuals earn the same level of
national income). Given its feature, that index is
widely used in statistics literature because it renders
better the concentration measurement in concrete
situations and it is specially suitable for comparing
the degree of concentration among heterogeneous
situations. The Gini index at national level was
calculated on the basis of the number of registered
domain names, and it resulted 0.91, and so higher
than in 2005, indicating that it is not possible to state
that, in Italy, only one Registrar registers all the
domain names under the ccTLD “.it”. However, the
value 0.91 is justified by the fact that only 10
registrars out of 1,842 register 63.83% of total
domain names. In 2005, 10 registrars out of 2,552
registered 46.30% of domain names. Therefore both
the indexes show that the concentration of domain
names registered by Registrars, from 2005 to 2010,
was increased. The analysis of concentration
resulted more clear when, in particular, the three
macro-areas North, Center and South were analyzed.
In all three areas, both indexes are increased (Tables
2 and 3. However, especially in the Centre of Italy,
the Gini index and the HHI in 2010 increased
considerably. In particular, HHI increased almost
twice, comparing data of 2010 with those of 2005.
This depends on the fact that, in such period, the
number of Registrars of the Center decreased while
the number of registered domains increased, and
also because the gap among Registrars in the
registration of domain names increased. In fact, in
2010 the Range (the difference between the
minimum and maximum of domains registered by
Registrars) is higher than in 2005 (Tables 2 and 3).
The Gini index of 0.96, in 2010, indicated that only
few Registrars register the total amount of domain
names under the ccTLD .it. As a matter of fact,
analyzing the data at an individual level, in the
Center, only two Registrars out of 427 register more
than 70% of domain names, 74.17% out of the total
amount of domain names. In 2005, two Registrars
out of 561 registered more than half the domain
names, 55.10% out of the total amount of domain
names. The North, on the contrary, is the region in
which there is more competition compared to the
other macro-areas and, as resulted, the two
concentration indexes are lower than in the Center
and in the South: the Gini is 0.80 and HHI is 228.78,
Table 2: Analysis of concentration of domain names “.it”
registered by Registrars 31-12-2005.
Macro
Area
Gini
Index
HHI
Index
Registrar
Domain
names
Range
North
0.78
103.51
1575 334350 14313
Centre 0.93 1838.44 561 544874 210255
South 0.83 940.84 416 155275 39747
Italy 0.87 542.75 2’552 1034499 210255
Table 3: Analysis of concentration of domain names “.it”
registered by Registrars 31-12-2010.
Macro
Area
Gini
Index
HHI
Index
Registrar
Domain
names
Range
North 0.80 228.78 1101 486322 43183
Centre 0.96 3468.80 427 1118659 617753
South 0.86 1190.19 314 181109 42942
Italy 0.91 1389.92 1’842 1786090 617753
in 2010. Even if the HHI results to be higher than
2005, since the Registrars have registered more than
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595