When it comes to cities, the word sustainable comprises much more than the environmental connotation acquired in recent decades. As any cement-pounding city dweller can attest, sustainable applies to basic living conditions, as well as environmentally-friendly practices. So it makes sense to assess cities’ sustainability in terms of residents. After all, what qualifies a city as a city, if not for the people?

Cities must not only retain but attract people: to persist and grow, to pay for services provided, and even to turn a profit. So it also makes sense to score cities on financial stability.

And beyond its residents and economic standing, cities have to adapt. In the current climate, that urban adaptation often takes the form of environmental policy.

So while cities have been coined green and smart, what really makes a city sustainable?

Recent surveys generally give scores in three categories: people, planet, and profit, according to Arcadis’s Sustainable Cities Index, assembled by the London-based Center for Economics and Business Research. No city has managed to perfectly balance these three tentpoles yet. As more and more people gravitate toward urban centers, that sweet spot remains a moving target. Factors like population growth and climate change affect a city’s sustainability score from year-to-year, and though circumstances seem to primarily impact one target, the three are closely intertwined. Hence, the Sustainable Cities Index, intended to reflect a city’s overall health: “not to create a hierarchy of elite cities,” emphasizes John Batten, Arcadis’s Global Director of Water and Cities, “but to indicate areas of opportunity.”

The necessity of comparison brings us back to examination of the term city. Although you can compose a checklist of characteristics that constitute a city, no entity of that name will reflect those characteristics in quite the same way. In a column tracking minimum population, for example, you may see similar numbers, but not the wildly varying demographics they represent.

Again, John Batten puts these statistics in perspective: “‘Cities have unique identities that are heavily influenced by their cityscape, economy and culture. Some cities, particularly established European cities such as Zurich which tops our index, are positioned within a moderate climate and have an economically balanced population which gives them a clear advantage when it comes to their sustainability. Others have to deal with issues including extreme climates, rapid urbanization and lack of financial resources which can hold them back.’”

So, with all these disclaimers about awarding cities of all shapes and sizes with number scores that constitute a somewhat arbitrary measure of sustainability, how can these cities take cues from each other? Specifically, what can the relatively high-scoring New York City learn from the similarly successful Toronto?

The Sustainable Cities Index operates on a scale from 100, and Zurich tops the charts with a score near 75. New York is ranked overall 26th out of 100 cities surveyed, and Toronto comes in at 33rd. However, the cities’ scores are not far off from each other: New York scored 62.9% overall, and Toronto 61.7%. And while New York earned the title of most sustainable North American city for 2016, Toronto held that title in 2015, for the first Sustainable Cities Index report.

The cities’ sub-scores reveal a more detailed makeup: in the people category, Toronto actually beat New York, with a sub-score of 62.3% compared to New York’s 53.4%, placing them 40th and 77th out of 100 cities. They scored similarly in the planet section: Toronto at 68.1% and New York at 66.1%, ranking 28th and 33rd in this category. The profit category explains why New York outranks Toronto on the Index: New York scored 69.3% in this category and Toronto scored 54.8%, leaving them at 8th and 38th in this section.

So if New York is to look to Toronto for ways to improve its sustainability score, the planet and particularly the people sub-scores give some indication. Each city’s rating in the people sub-section is comprised of scores in several sub-categories: education, health, demographics, income inequality, affordability, work-life balance, and crime. The biggest discrepancies between Toronto and New York can be found in income inequality (10.7% > 6.5%); crime (13.2 % > 10.1%); and affordability (7.1% > 0.2%).

The planet sub-score is based on environmental risks, green spaces, energy, air pollution, greenhouse gas emissions, waste management, drinking water and sanitation. The most significant differences between Toronto and New York here are environmental risks (9.9% > 7.6%); energy (8.6% > 6.5%); and air pollution (13.4% > 12.1%).

Toronto has been especially successful in energy efficiency, waste management, and water. Toronto is one of the top three cities for ensuring a robust, effective, and healthy water supply, while New York’s resources are considered more vulnerable. Indeed, the report highlights some of New York’s perceived weaknesses, including poverty, an overburdened transportation infrastructure, and rising sea levels forecasting more storms, flooding, and other natural disasters.

Toronto, on the other hand, will have to deal with a 25% population increase expected in the next 15 years. “According to a report presented by the city, Toronto has reduced greenhouse gas emissions by 25% since 1990 and expects to improve that number to 30% by 2030 even amid the city`s population growth, which has seen the metropolitan area swell to six million as of February 2015.”

Hopefully these sustainability assessments and metrics encourage cities around the globe to learn from each other and the myriad issues faced by such complex cosmopolitan organisms in the coming century.