does anyone know how to compute the International Competitive Advantage Index (ICA) in Stata? For example, if we would have the following dataset (Note: It is not in -dataex-, but that is because I do not have this data in Stata yet):

A | B | ICA |

1 | 10 | 1.25 |

1 | 10 | 1.25 |

1 | 20 | 0.83 |

1 | 30 | 0.83 |

2 | 20 | 1.67 |

2 | 30 | 1.67 |

3 | 10 | 1.25 |

3 | 20 | 0.83 |

3 | 30 | 0.83 |

3 | 10 | 1.25 |

ICA_ab = (C_ab / C_b) / (C_a / C_n)

where

C_ab = is the number of observations of variable A for a given observation b of variable B.

C_b = is the total number of observations b of variable B.

C_a = is the total number of observations a of variable A.

C_n = is the total number of observations (number of rows).

To make this clear, these variables would take on the following values for the first ICA index:

C_ab = 2 (because the 10 exists twice for all the 1s in variable A)

C_b = 4 (there are four 10s in variable B)

C_a = 4 (there are four 1s in variable A)

C_n = 10 (there are 10 rows)

Hence, the ICA for the first row computes to 1.25.

I would appreciate any help. Thank you very much.

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