Vietnam's capital city joined Moscow in Russia, Belgrade in Serbia, Kiev in Ukraine and Abidjan in the Ivory Coast as the top five cities in the world in making improvements to their overall livability rankings, according to the research and analysis division (EIU) of the Economist Group.

Hanoi, currently home to eight million, scored 59.7 out of 100, the EIU says in its Global Livability Index 2019 report. Compared to five years ago, Hanoi's score has jumped by 5.5 percentage points.

The EIU's index ranks 140 cities on 30 factors bunched into five categories: stability, health care, culture and environment, education and infrastructure.

The livability score is reached through category weights, which are equally divided into relevant subcategories to ensure that the score covers as many indicators as possible. Indicators are scored as acceptable, tolerable, uncomfortable, undesirable or intolerable. These are then weighted to produce a rating, where 100 means that livability in a city is ideal and 1 means that it is intolerable.

The EIU report said that over the last five years, Hanoi has made improvements almost across the board, with higher stability, culture, education and infrastructure scores.

This is the second year in a row Hanoi has made it to the group of five biggest improvers in the EIU ranking. Last year, Ho Chi Minh City was also part of the group.

Austrian capital Vienna retained its top position on the index this year, scoring a near-perfect 99.1 out of 100, ahead of Australia's Melbourne with 98.4 and Sydney with 98.1.

Japan's Osaka and Tokyo are the only Asian representatives in the top ten.

The three least livable cities in the ranking are Damascus of Syria which scores 30.7, Lagos of Nigeria with 38.5 and Dhaka of Bangladesh with 39.2.

The report said that for the first year, the effects of climate change were seen impacting livability.

"A slew of cities in emerging markets that are among the most exposed to the effects of climate change have seen their scores downgraded," it said. These include New Delhi in India, which suffers from poor air quality, Cairo in Egypt and Dhaka in Bangladesh.

"A lack of a concerted global effort to tackle climate change risks further downward revisions in these scores, threatening to offset improvements in the other categories, such as education and infrastructure, which remain on a broadly upward trend," the report said.