Real estate is an ever-changing, competitive space that’s often dictated by the needs and wants of consumers. One of the new trends shaping the industry is the demand for the 18-hour city.

The Urban Land Institute and PwC produce a yearly report titled Emerging Trends in Real Estate. Twenty years ago, this report coined two labels to be applied to cities: 9-5 cities and 24-hour cities. The 9-5 cities are often smaller and revolve around business. People go there solely to work, living and playing elsewhere. Examples of these cities are Hartford, CT or Dallas, TX. Twenty-four hour cities, on the other hand, are alive at all hours. It’s a city in which people live, work, and play. These cities include New York and Chicago.

In 2015, ULI and PwC has made an addition to their two categories: 18-hour cities. Data shows that more and more consumers are seeking a middle ground between the smaller, quiet 9-5 cities and the chaotic, always-going 24-hr cities. Eighteen-hour cities are still liveable and vibrant, but quiet down in the late hours.

The key to an 18-hour city is a strong downtown core. Although many of these cities tend to be smaller, the revitalized downtown area is what allows them to escape the 9-5 label. This includes having plentiful restaurants, bars, and shopping as well as sufficient housing. Many former 9-5 cities are in the midst of bettering their downtown, and consequently becoming 18-hour cities. Cities such as Boston, Minneapolis, and Denver are undergoing this transformation.

So, why this sudden focus on downtowns? It can be argued that this shift is largely due to a concept called New Urbanism. New Urbanism refers to a movement pushing for walkable neighborhoods and the trend of people, especially young people remaining in cities, rather than moving to the suburbs.

ULI and PwC found in this report that there are quite a few reasons for this demand for 18-hour cities. One big factor is cost. Many people want the urban experience without the costs of renting in, say, Midtown Manhattan or the trendier neighborhoods in Boston. Smaller, more up-and-coming cities are often cheaper, but still offer many of the same amenities as the 24-hour cities. It is also interesting to note that this trend isn’t limited to Millennials: PwC found that many of those moving to 18-hour cities are baby boomers because not only is it cheaper to live in these cities, but also cheaper to do business.

It’s often hard to predict where the market is heading, but 18-hour cities looks to possibly be the next big trend in 2015.