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Building Ownership Matrices Example

import pyblp
import numpy as np

np.set_printoptions(threshold=100)
pyblp.__version__

'1.1.0'

In this example, we’ll use the IDs created in the building ID data example to build a stack of standard ownership matrices. We’ll delete the first data row to demonstrate what ownership matrices should look like when markets have varying numbers of products.

id_data = pyblp.build_id_data(T=2, J=5, F=4)
id_data = id_data[1:]
standard_ownership = pyblp.build_ownership(id_data)
standard_ownership

array([[ 1.,  0.,  0.,  0., nan],
       [ 0.,  1.,  0.,  0., nan],
       [ 0.,  0.,  1.,  0., nan],
       [ 0.,  0.,  0.,  1., nan],
       [ 1.,  1.,  0.,  0.,  0.],
       [ 1.,  1.,  0.,  0.,  0.],
       [ 0.,  0.,  1.,  0.,  0.],
       [ 0.,  0.,  0.,  1.,  0.],
       [ 0.,  0.,  0.,  0.,  1.]])

We’ll now modify the default \(\kappa\) specification so that the elements associated with firm IDs 0 and 1 are equal to 0.5.

def kappa_specification(f, g):
    if f == g:
       return 1
    return 0.5 if f < 2 and g < 2 else 0

We can use this specification to build a stack of alternative ownership matrices.

alternative_ownership = pyblp.build_ownership(id_data, kappa_specification)
alternative_ownership

array([[1. , 0.5, 0. , 0. , nan],
       [0.5, 1. , 0. , 0. , nan],
       [0. , 0. , 1. , 0. , nan],
       [0. , 0. , 0. , 1. , nan],
       [1. , 1. , 0.5, 0. , 0. ],
       [1. , 1. , 0.5, 0. , 0. ],
       [0.5, 0.5, 1. , 0. , 0. ],
       [0. , 0. , 0. , 1. , 0. ],
       [0. , 0. , 0. , 0. , 1. ]])

In addition to specifying a custom function, there are also a couple of special case strings that efficiently construct monopoly and single-product firm ownership matrices.

monopoly_ownership = pyblp.build_ownership(id_data, 'monopoly')
monopoly_ownership

array([[ 1.,  1.,  1.,  1., nan],
       [ 1.,  1.,  1.,  1., nan],
       [ 1.,  1.,  1.,  1., nan],
       [ 1.,  1.,  1.,  1., nan],
       [ 1.,  1.,  1.,  1.,  1.],
       [ 1.,  1.,  1.,  1.,  1.],
       [ 1.,  1.,  1.,  1.,  1.],
       [ 1.,  1.,  1.,  1.,  1.],
       [ 1.,  1.,  1.,  1.,  1.]])

single_ownership = pyblp.build_ownership(id_data, 'single')
single_ownership

array([[ 1.,  0.,  0.,  0., nan],
       [ 0.,  1.,  0.,  0., nan],
       [ 0.,  0.,  1.,  0., nan],
       [ 0.,  0.,  0.,  1., nan],
       [ 1.,  0.,  0.,  0.,  0.],
       [ 0.,  1.,  0.,  0.,  0.],
       [ 0.,  0.,  1.,  0.,  0.],
       [ 0.,  0.,  0.,  1.,  0.],
       [ 0.,  0.,  0.,  0.,  1.]])