After being recognized as the country with the largest economy in Africa, Nigeria is now ranked as the top economy that American and European multinational companies are most interested in.

Nigeria is joined by Argentina and Vietnam as the frontier markets that multinational corporations are most interested in, according to a new index of corporate sentiment.

This ranking was derived from “The Frontier Markets Sentiment Index”, created exclusively for the Wall Street Journal by Washington DC-based advisory firm Frontier Strategy Group.

The index tracks the level of interest shown by major European and American multinational companies in countries across the frontier markets world.

The report is based on information collected from FSG’s over 200 multinational clients, which include companies like General Electric, Coca-Cola, and Novartis.

The index is a based on information collected from FSG’s roughly 200 multinational clients, which include companies such as Coca-Cola KO -0.12%, General Electric GE +0.30%, Novartis NOVN.VX +0.19%, Dell and Akzo Nobel AKZOY -0.97%.

Matt Lasov, FSG’s global head of advisory and analytics, explains how the index works: “We collect data about which countries the companies are watching for potential future investment.

Over time, that gives us a clear picture of their market priorities—which countries are they including in their future plans and which they are dropping.”

The research provides two key insights: the current state of sentiment toward countries in the frontier markets, and the change in sentiment over time.

Corporate sentiment is calculated as the percentage of companies that include a particular country on their watch-list. If 50 of the 200 companies are keeping an eye on a particular country, the sentiment index score would be 25%.