Overview Granovetter: Strength of Weak Ties What are ‘weak ties’? why are they ‘strong’? Burt: Structural Holes What are they? What do they do? How do they work? “Good Ideas” Methods & Measures: 1) Moving data around SAS Data steps 2) Calculating Ego-Network Measures From Ego-network modules From Global Networks tructural Holes & Weak Ties
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Overview Granovetter: Strength of Weak Ties What are ‘weak ties’? why are they ‘strong’?
Structural Holes & Weak Ties. Overview Granovetter: Strength of Weak Ties What are ‘weak ties’? why are they ‘strong’? Burt: Structural Holes What are they? What do they do? How do they work? “Good Ideas” Methods & Measures: 1) Moving data around SAS Data steps - PowerPoint PPT Presentation
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OverviewGranovetter: Strength of Weak Ties
What are ‘weak ties’?why are they ‘strong’?
Burt: Structural HolesWhat are they?What do they do?How do they work?
“Good Ideas”
Methods & Measures:1) Moving data around
SAS Data steps2) Calculating Ego-Network Measures
From Ego-network modulesFrom Global Networks
Structural Holes & Weak Ties
Granovetter argues that, under many circumstances, strong ties are less useful than weak ties. Why?
Redundancy
Local Density, Global Fragmentation
Structural Holes & Weak Ties
What are the implications?
For individuals?
For Communities?
Structural Holes & Weak TiesThe Strength of Weak Ties
Structural Holes & Weak TiesStructural Holes
Burt. Structural Holes
Similar idea to SWT: Your ties matter because of who your connects are not connected to.
What is (for Burt) Social Capital?Relationships with other players
Why does it matter?
“Social capital is as important as competition is imperfect and investment capital is abundant.”
A structural Hole is a buffer: a space between the people you are connected to.
2 ways:CohesionStructural Equivalence
Structural Holes & Weak TiesStructural Holes
EfficiencyMaximize the number of non-redundant contacts
EffectivenessDraw your primary contacts from different social worlds
Structural Holes & Weak TiesStructural Holes
Number of Contacts
Num
ber
of N
on-R
edun
dant
Con
tact
s
Maximum Efficiency
Minimum Efficiency
Decreasing Efficiency
Increasing Efficiency
Structural Holes & Weak TiesStructural Holes
Difference between SWT & SH:
Burt’s claim is that he focuses directly on the causal agent active in Granovetter.
(but note the footnote in “good ideas,” where he says the effect is not causal).
Structural Holes & Weak TiesStructural Holes
Structural Holes & Weak TiesGood Ideas
The hypothesis is that those who broker different groups are exposed to different ideas and thus more likely to have a good idea.
Uses data on discussions among managers in a large electronics firm.
Structural Holes & Weak TiesGood Ideas
Burt’s idea discussion network
Structural Holes & Weak TiesGood Ideas
Burt’s idea discussion network
Structural Holes & Weak TiesGood Ideas
Figure 3: Core network in the supply chain
With headquarters
Structural Holes & Weak TiesGood Ideas
Figure 3: Core network in the supply chain
Without headquarters
Structural Holes & Weak TiesGood Ideas
The results show a strong effect of network constraint on salary, evaluation and promotion, independent of the job/age characteristics related to human capital explanations.
Structural Holes & Weak TiesGood Ideas
The results show a strong effect of network constraint on salary, evaluation and promotion, independent of the job/age characteristics related to human capital explanations.
Structural Holes & Weak TiesGood Ideas
Calculating the measures
Burt discusses 4 related aspects of a network:1) Effective Size2) Efficiency3) Constraint4) Hierarchy
Structural Holes & Weak TiesCalculations
Effective Size
Conceptually the effective size is the number of people ego is connected to, minus the redundancy in the network, that is, it reduces to the non-redundant elements of the network.
Effective size = Size - Redundancy
Structural Holes & Weak TiesCalculations
Effective SizeBurt’s measures for effective size is:
j qjqiqmp1
Where j indexes all of the people that ego i has contact with, and q is every third person other than i or j.
The quantity (piqmjq) inside the brackets is the level of redundancy between ego and a particular alter, j.
Structural Holes & Weak TiesCalculations
Effective Size:
j qjqiqmp1
Piq is the proportion of actor i’s relations that are spent with q.
mjq is the marginal strength of contact j’s relation with contact q. Which is j’s interaction with q divided by j’s strongest interaction with anyone. For a binary network, the strongest link is always 1 and thus mjq reduces to 0 or 1 (whether j is connected to q or not - that is, the adjacency matrix).
The sum of the product piqmjq measures the portion of i’s relation with j that is redundant to i’s relation with other primary contacts.
Efficiency is the effective size divided by the observed size.
Structural Holes & Weak TiesCalculations
1
2
4 5
3
Constraint
Conceptually, constraint refers to how much room you have to negotiate or exploit potential structural holes in your network.
“..opportunities are constrained to the extent that (a) another of your contacts q, in whom you have invested a large portion of your network time and energy, has (b) invested heavily in a relationship with contact j.” (p.54)