What is the first thing you notice when you walk into a shop? The products displayed at the entrance? Or the soft background music?

But have you ever noticed the smell? Unless it is bad, the answer is likely to be no. But while a shop’s scent (香味) may not be outstanding compared with sights and sounds, it is certainly there. And it is proving to be an increasing powerful tool in encouraging people to purchase.

A brand store has become famous for its distinctive (独特的) scent which floats through the fairly dark hall and out to the entrance, by scent machines. A smell may be attractive but it may not just be used for freshening air. One sports goods company once reported that when it first introduced scent into its stores, customers’ intention to purchase increased by 80 percent.

But while e-shops can only use sights and sounds, bricks-and-mortar stores (实体店) can offer a full experience from the minute customers step through the door to the moment they leave. Another brand store seeks to be much more than a shop, but rather a destination. And scent is just one way to achieve this.

Now a famous store uses complex man-made smell to make sure that the soft scent of baby powder floats through the kid department, and coconut (椰子)scent in the swimsuit section. A department store has even opened a new lab, inviting customers on a journey into the store’s windows to smell books, pots and drawers, in search of their perfect scent.

Buy land, advised Mark Twain； they're not making it any more. In fact, land is not really scarce: the entire population of America could fit into Texas with more than an acre for each household to enjoy. What drives prices rocket is a collision between uncontrolled demand and limited supply in the great metropolises like London, Mumbai and New York. In the past ten years real prices in Hong Kong have risen by 150%. Residential（住宅的）property in Mayfair, in central London, can go for as much as £55,000（$82,000）per square metre. A square mile of Manhattan residential property costs $16.5 billion.

Even in these great cities the scarcity is artificial. Regulatory limits on the height and density（密度）of buildings constrain（限制）supply and increase prices. A recent analysis by academics at the London School of Economics estimates that land-use regulations in the West End of London inflate the price of office space by about 800%; in Milan and Paris the rules push up prices by around 300%. Most of the enormous value captured by landowners exists because it is almost impossible to build new offices to compete those profits away.

The costs of this misfiring property market are huge, mainly because of their effects on individuals. High housing prices force workers towards cheaper but less productive places. According to one study, employment in the Bay Area around San Francisco would be about five times larger than it is but for tight limits on construction. Add up these costs in lost earnings and unrealized human potential, and the figures become dizzying. Lifting all the barriers to urban growth in America could raise the country's GDP by between 6.5% and 13.5%, or by about 1 trillion—2 trillion. It is difficult to think of many other policies that would produce anything like that.