---
title: "Exponentially Weighted Moving Average (EWMA) Value At Risk"
method: POST
path: "/portfolios/analysis/value-at-risk/forecast/arma-ewma"
tags: ["Portfolio Analysis / Risk Measures / Value At Risk Forecast"]
---

# Exponentially Weighted Moving Average (EWMA) Value At Risk

`POST /portfolios/analysis/value-at-risk/forecast/arma-ewma`

## Request

- Base URL: `https://api.portfoliooptimizer.io/v1`
- URL: `https://api.portfoliooptimizer.io/v1/portfolios/analysis/value-at-risk/forecast/arma-ewma`
- Auth: API key in header `X-API-Key`

Forecast the value at risk of a portfolio, assuming the portfolio logarithmic returns follow an Exponentially Weighted Moving Average (EWMA) conditional variance model, coupled with an AutoRegressive Moving Average (ARMA(1,1)) conditional mean model.

References
* [Christoph Hartz, Stefan Mittnik, Marc Paolella, Accurate value-at-risk forecasting based on the normal-GARCH model, Computational Statistics & Data Analysis, Volume 51, Issue 4, 2006, Pages 2295-2312](https://www.sciencedirect.com/science/article/abs/pii/S0167947306003367)
* [RiskMetrics Group. Longerstaey, J. (1996). RiskMetrics technical document, Technical Report fourth edition](https://www.msci.com/documents/10199/5915b101-4206-4ba0-aee2-3449d5c7e95a)

## Request body

- object
  - `confidenceLevel` number: The confidence level
  - `portfolios` object[], required
    - `portfolioValues` number[], required: portfolioValues[t] is the value of the portfolio at the time t
    - `portfolioReturnsConditionalMeanModel` 'zeroMean' | 'constantMean' | 'ar1Mean' | 'arma11Mean': The conditional mean model for the portfolio logarithmic returns
    - `portfolioReturnsStandardizedResidualsDistribution` 'normal' | 'student': The assumed distribution for the portfolio logarithmic returns standardized residuals

## Response `200`

OK

- object
  - `portfolios` object[], required
    - `portfolioValueAtRisk` number, required: The empirical value at risk of the portfolio, in (logarithmic return) percentage
    - `portfolioArithmeticValueAtRisk` number, required: The empirical value at risk of the portfolio, converted from logarithmic return percentage to arithmetic return percentage

## Changes

- **2026-02-08** `ac51d393c9a9`: 1 info
  - endpoint added

[Operation history](https://skmtc.dev/portfoliooptimizer/apis/portfolio-optimizer/changes/portfolios/analysis/value-at-risk/forecast/arma-ewma/post.md)

---

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