According to the Forbes 2021 Worlds Billionaires List and widely reported business news, which city had the highest number of billionaires in the world at that time?

Introduction / Context:
The number of billionaires concentrated in a city is often used as an indicator of global wealth hubs. Business magazines such as Forbes publish annual lists that rank cities by how many billionaires they host. In 2021, Forbes reported that Beijing had overtaken New York City to become the city with the most billionaires in the world, a fact that quickly appeared in many current affairs and general knowledge compilations.

Given Data / Assumptions:
- The reference point is the Forbes 2021 Worlds Billionaires List.- We must identify which city had the highest number of billionaires that year.- Options include New York City, Beijing, Moscow, and London.- Rankings can change over time, so the year mentioned is important.

Concept / Approach:
In many earlier years, New York City was frequently at the top for number of billionaires, with Moscow and other cities sometimes competing. However, in the 2021 Forbes list, Beijing was highlighted as having slightly more billionaires than New York City, due to rapid growth in technology and internet based fortunes in China. Therefore, although New York City remained a major wealth centre, Beijing took the number one position in that specific year.

Step-by-Step Solution:
Step 1: Recognise that the question is time bound and refers specifically to the 2021 Forbes list.Step 2: Recall media coverage stating that Beijing overtook New York City in the number of billionaires according to Forbes in 2021.Step 3: Compare options. New York City is a traditional favourite but was second in the 2021 list.Step 4: Moscow and London have large concentrations of wealthy individuals but did not top the Forbes city ranking for billionaires in that year.Step 5: Therefore, Beijing is the correct city that had the highest number of billionaires according to the 2021 Forbes Worlds Billionaires List.

Verification / Alternative Check:
News reports summarising the 2021 Forbes list explicitly stated that Beijing now had more billionaires than any other city and that it had overtaken New York City. This change was presented as a symbol of Chinas rapid economic growth and the rise of its tech entrepreneurs.

Why Other Options Are Wrong:
New York City: Previously the top city for billionaires, but in the 2021 Forbes list it was second behind Beijing.Moscow: Has many billionaires, especially in energy and natural resources, but it did not top the 2021 ranking.London: An important financial centre, yet not the city with the maximum number of billionaires in the 2021 list.

Common Pitfalls:
Many learners remember older facts that New York City had the most billionaires and do not update their knowledge when new rankings are released. Others pay attention only to country level lists, like which country has the most billionaires, and ignore city specific data. The key is to read the year mentioned in the question carefully and to regularly revise updated economic facts.

Final Answer:
Beijing had the highest number of billionaires in the world according to the Forbes 2021 Worlds Billionaires List.