# Default Probability Table

From Open Risk Manual

## Definition

A **Default Probability Table** (DPT) is a mapping from Credit Score ranges or Credit Ratings to a Probability of Default.

### Credit Score DPT

A continuous score DPT are defined via:

- the number of score ranges
- the boundaries of the score ranges

### Credit Rating DPT

A Credit Rating System DPT is simply a map from rating classes to default probabilities

## Example

A hypothetical mapping table for a credit score system producing scores from 0 to 1000 which is being mapped to 10 distinct probabilities of default

Credit Score Range | Probability of Default |
---|---|

910 and above | 0.2% |

810 - 900 | 1.0% |

710 - 800 | 2.0% |

610 - 700 | 4.0% |

510 - 600 | 5.0% |

410 - 500 | 6.0% |

310 - 400 | 10.0% |

210 - 300 | 12.5% |

110 - 200 | 15.0% |

Below 100 | 20.0% |

## Issues and Challenges

- A default probability table is effectively a Risk Model, that is, it predicts the likelihood of certain events according implied Model Assumptions (for example the selection of ranges). As such it is distinct from the Empirical Transition Matrix that expresses the
*actually realized*event rates for score ranges or rating categories