Why do houses in Vancouver neighborhoods with a high percentage of Chinese residents tend to sell for more when the house number ends in 8? And why do they sell for less when the house number ends in 4?

According to a study from the University of British Columbia, when the number on the house ended in 4, houses sold at a 2.2 percent discount. The reason, according to UBC: In Mandarin, Cantonese and several other Chinese dialects, the pronunciation of the number four sounds very similar to the word for "death."

There's even a name for the fear of No. 4: It's called tetraphobia. And it's why Richmond Hill, Ont., passed a bylaw this summer outlawing the number four in all new street numbers.

At the same time, when the number above the door ends in 8, which is phonetically similar to the word for "prosperity" or "wealth" in many Asian tongues, the house tended to sell for a 2.5 percent premium.

Gamblers are often superstitious, which is why you'd be hard-pressed to find a decent-sized casino hotel in Las Vegas with floor numbers four, 14, 24, 34 and 40 to 49. And of course, numerous office buildings throughout the country do not have a 13th floor.

Home sellers may not be afraid of certain numbers, at least not all of them. But according to real estate search engine Trulia, setting a price and "lucky" numbers go hand-in-hand.

"Setting the right asking price for your home isn't all science and it isn't all art," says Jed Kolko, Trulia's chief economist. "Sellers and agents pick numbers to signal their strategy, and to appeal to the traditions and superstitions of local buyers."

After studying the asking prices of all the homes for sale on the Trulia site for about a year starting in October 2011, Kolko discovered that after zero, as in $200,000, the number nine was the most popular, as in $199,999.

That is, of the non-zero ending digits in list prices, a whopping 53 percent of all prices ended in nine. The next most common number was five. "No other digit comes close to 9 and 5," Kolko says.

As it turns out, nine, in the vernacular of home buyers and sellers, is less than zero -- by more than $1.

And when house prices are reduced, according to the Trulia study, the lower price is more likely to have nine as the final non-zero digit than it was in the original price. In other words, the economist reports, when sellers are more eager to sell, they are more likely to price with a nine than, say, a one or two.

But apparently it's only sellers of lower-cost homes who subscribe to this pricing theory. When houses are priced over $1 million, buyers can't be fooled into thinking they have nailed a bargain with just one digit. Which is why only one in four homes listed for seven figures or more had a nine as the last number.

At the same time, it appears that nine is only popular in some markets. In upstate New York, for example, nine was the last non-zero digit in more than two-thirds of the listings. But nine was in less than a third of the listings in places like El Paso, Texas; Tacoma, Wash., Seattle and Honolulu.

Triskaidekaphobia -- fear of the number 13 -- is much more widespread. It appeared in the asking price of just 13 percent of Trulia's listings. That's not just at the end of the asking price, but anywhere in it. The number 13 appeared in home prices less than the numbers 12 and 17.

Then, of course, there's lucky number seven. House prices in Nevada are more likely to have a seven in the list price than anywhere else in the country. And whereas prices with triple sevens were found in just eight out of every 10,000 listings in the Trulia study, such a combination is three times more likely in the Silver State.

The numbers three and six represent both the good and bad in Christian numerology. And as you may have guessed, they resonate most in the Bible Belt, which covers most of the South.

The number 316, as in John 3:16, was 27 percent more likely to appear somewhere in a Bible Belt home's asking price than in houses elsewhere.

And good wins out over evil, at least when pricing a house, for the number 666 showed up in less than one out of every 10,000 listings. But 666 was still more common in Bible Belt houses than anywhere else.

Back to the number eight: It's so important in Chinese culture that the Beijing Olympics officially began at 8:08:08 p.m. on Aug. 8, 2008 (8/8/08), and that the United Airlines flight from San Francisco to Beijing is numbered 888.

Same thing for house prices. In neighborhoods without a large Asian population, Trulia found that the number eight was the last non-zero numeral in just 4 percent of the listings. But in neighborhoods with a preponderance of Asian residents, eight was the last non-zero digit in 20 percent of the listings.

Most people spend more than 50 percent of their time indoors -- children, some 90 percent -- so it is important to pay attention to the quality of the air in your home. And that means more than installing a few carbon monoxide detectors or testing for radon.

Mold can cause severe health problems, for example. Ditto for lead, a tainted water supply or hazardous household products. And since government at the state and federal levels can only legislate so much, it is up to homeowners to take whatever action is necessary to protect their families.

Indoor air pollutants come not only from what people have in their homes but also what they do there. It is well established, for example, that smoking can cause breathing problems. But so can furry pets and home projects that involve sanding, welding, painting or solvent chemicals like varnish and paint strippers.

Fortunately, there are simple steps you can take to find out the causes of poor indoor air quality and what to do about them.

-- Mold, sometimes known as mildew, grows where there are wet or damp surfaces. You can spot it easily when it grows out in the open, but often it is hidden behind walls or under the carpet. Either way, the telltale signs are the same: musty smells, watery eyes, runny noses, sneezing, itching, wheezing, headaches and fatigue.

To protect against mold, be sure your gutters are clean and not leaking, and that downspouts direct rainwater away from the house. Your yard should slope away from the building.

Repair leaking roofs, walls, doors and windows right away. Water is insidious, and can cause problems if left to stand. If your carpet remains wet for more than a couple of days, for example, it is best to toss it. It's also wise not to leave water standing in refrigerator drip pans.

Additionally, make sure the humidity in your home is not too high. If the moisture content in the air is more than 50 percent, turn off your humidifier and move your jungle of houseplants outside. Always make sure to run your bathroom fan when bathing or showering, and run your kitchen exhaust fan when cooking.

-- Unlike mold, you can't see, smell or feel carbon monoxide (CO), a deadly gas that can make you sick or even kill you. Signs of low-level CO poisoning include headaches, nausea, vomiting, dizziness, sleepiness, tightness in the chest and difficulty breathing. Many people confuse it with the flu.

To protect your house and family, install carbon monoxide alarms near each sleeping area and on each floor. But to make sure they never go off, never use the kitchen stove or oven to heat your house, and call a repair service if the flame on your range's gas burners is orange or yellow.

Also, don't use charcoal grills or run car engines inside your house, garage or basement -- even for a short time. They produce so much CO that even opening the windows and doors will not give you enough fresh air. In the same vein, never warm a vehicle while it sits inside the garage, even with the garage doors open. Start lawnmowers, snowblowers and other yard equipment outside, never inside.

At least once a year, hire a heating contractor to check your furnace, vents and other sources of carbon monoxide. Make sure your fireplace chimney is clean and in working order with an annual checkup.

-- Lead poisoning poses a serious health risk for children. Lead is not used as much in paint, pipes and other materials as it once was -- indeed, lead paint was banned in 1978 -- so houses built prior to 1950 are the most problematic.

If you are planning to remodel your older home, or have just finished a renovation, beware of dust or paint chips. Otherwise, look for cracking, chipping or flaking paint, or doors or window frames where paint is being rubbed away.

Also check for lead pipes, which are a dull gray in color and scratch easily with a key or penny, or pipes which are joined with lead solder. Water that flows through them can contain lead.

Your state or local health department can tell you how to check for lead at little or no cost, and most hardware stores carry low-cost lead testing kits. But if you find lead, don't try to remove it yourself. Getting rid of lead in the wrong way can make the problem worse, so find a certified contractor for the job.

-- Public drinking water is safe, but if you have a well or other private water supply, it's up to you to protect yourself. And since you can't see, smell or taste potentially dangerous microbes, you should have your H2O tested about every two years for bacteria, nitrates and perhaps pesticides at a laboratory.

You should also take care of your well. Have it checked by a professional if it is more than 20 years old. Make sure there are no gaps between the well casting and the material or ground around it.

-- When it comes to hazardous household products, buy only what you need, and read and follow the directions. Properly dispose of what you don't use, or give the leftovers to someone who can use it. Never burn or dump leftover containers.

Most of the information for the above comes from the Department of Agriculture's National Institute of Food and Agriculture (www.nifa.usda.gov). Other good sources include the Office of Healthy Homes within the Department of Housing and Urban Development (www.hud.gov/healthyhomes), the Environmental Protection Agency (www.epa.gov/iaq) and Healthy Indoor Air for American Homes (www.healthyindoorair.org).

Yapmo, an internal communication program designed to replace inefficient group communications, has unexpectedly found a niche in the real estate sector. Agents are using it to help sellers price their houses and, in some cases, to actually sell properties before they are listed.

Atlanta Fine Homes Sotheby's International hasn't sold any houses using the intuitive software program since switching to it in July as a way to streamline internal communication. But just the other day, says broker David Boehmig, an agent in his firm used it to properly price a potential listing so it would sell more quickly.

But Chicago's largest residential brokerage, @properties, has been using the system since Jan. 1. And in that time, Kevin Van Eck, director of agent development, estimates that 275 properties have been sold thanks to the software -- without ever being placed on the local multiple listing service.

The main purpose of the Yapmo -- techie shorthand for talk, or yap, mobile -- wasn't to validate pricing, or even sell houses. Rather, it was to replace ineffective company communication systems and allow emails to be used more effectively.

But it turned out that "it works extremely well" in the real estate sector, says Paul Everton, CEO of the Chicago software company. And as far as listings and sales go, Everton says, "It just hit me from left field."

Yapmo describes itself as a mobile software company which builds workflow tools that allow a company's employees to work more efficiently and communicate smarter. It claims its tools boost productivity, increase sales and accelerate ideas.

@properties bought into the program for just that reason. It went into business eight years ago implementing web- and email-based technologies that enabled the company to out-maneuver its competitors and become Chicago's largest brokerage, with 13 offices in the city and suburbs and some 1,200 agents.

But fast-forward to 2013, and the same technologies that allowed the company to move quickly and prosper have become a burden. Some emails, for example, were copied to 20 different people, whether they needed the messages or not. And in the process, key messages from company owners and brokers were getting lost.

"Emails have been a huge benefit in being able to collaborate," says Van Eck of @properties. "But now I get 300 a day and only four actually apply to me."

Yapmo says the typical employee spends 13 hours a week in their email inboxes, and real estate agents are no different. But by using the firm's intuitive software, @properties has been able to eliminate some 75,000 emails a year from every agent's inbox.

That means agents no longer have to fool with superfluous emails selling Viagra, unwanted notices about office pools, and other non-work-related messages. That frees them up to spend more time listing houses, showing and selling properties, and attending closings.

Agents found that the software allowed them to "preview" possible listings with their fellow agents, and market them internally before they hit the open market.

That's a form of so-called "pocket listings," which are somewhat controversial in and of themselves.

With a pocket listing, a property for sale is held out of the local MLS while the seller's agent shops it among his own list of clients and friends. If the agent finds a buyer, he gets to keep the entire commission rather than sharing it with a buyer's agent.

But while a house is in the agent's pocket, so to speak, it is not exposed to the entire market, as it would be if it was listed on the MLS. And in theory, at least, if the house was listed, the seller might have been able to secure a higher price.

Under the rules of most MLS systems, a property must be listed within 48 hours of receiving a signed listing agreement. So a true pocket listing is only a short-term ploy at best.

But the Yapmo software makes the process more efficient. Agents are able to automatically shop the property in-house directly to buyers and other agents who have expressed an interest in that kind of house, that price range or perhaps that particular location.

It isn't intended to limit exposure to keep the deal in-house, according to Van Eck. Rather, it is intended to maximize exposure during the "downtime" between when a listing is taken and the house is ready to show.

"Nothing in the MLS defines what people are looking for," says Boehmig, the Atlanta broker. "But with this tool, a conversation can ensue while a house is getting ready to come on the market. Our agents can say, 'I want to hear about that kind of stuff but not that kind of stuff.'"

Yapmo also works well for sellers who don't know what their homes are worth, or for those who value their privacy and don't want to tell the world that they are getting ready to put their properties on the market -- or what price they are asking.

"One of our agents just took a listing but was concerned about the price," says Boemig. "He was able to email other agents in the company saying, 'Here's what the seller is thinking. What do you think?' And when the house actually came on the market, it was positioned properly to sell."