Fixed interest rates for 30-year mortgages remain well below 4 percent, and industry observers predict they won't break 5 percent by the end of 2015.

Yet sales of both newly built and previously owned houses, while much improved since scraping bottom in 2010-11, remain well below average - because interest rates are just part of a home-buying decision.

In fact, national data reflecting the last 10 years of home sales - 2005 to 2014, including the mid-decade housing boom and bust - and the interest rates during that same period suggest that one has little to do with the other.

The recession that followed the bursting of the housing bubble in 2006-07 and the meltdown of the overall economy that began in September 2008 succeeded in bringing the housing market to a near-standstill.

Interest rates that were three percentage points lower during the economic downturn than they were at the peak of the market did little to get housing moving again, as the industry had hoped.

"Consumer confidence and the perception of the economy as a whole have a greater effect on residential real estate than whether the rates are at 4 percent or 6 percent," said Jeff Block of Berkshire Hathaway Home Services Fox & Roach Realtors, in Center City.

"Over the last 15 years, I saw the hottest market when rates were between 5.75 percent and 6.75 percent, 2003 to 2006," Block said, "and then the softest market when rates were mostly in the [4 percent area] and even lower from 2009 to 2012."

In forecasting what might occur this year, Greg McBride, chief financial analyst at Bankrate.com, which aggregates rate information for mortgages and other financial products, said, "As the year progresses and the Federal Reserve's timetable for interest-rate hikes comes into focus, mortgage rates will move higher," but no more than 4.75 percent."

Some even go as far as saying that rates will hover around 3.75 percent to 4.25 percent the entire year.

A slow rise in rates could stimulate buyers to act, said S. Clark Kendus of Weichert Realtors, in Media, noting, "As they see their prospective housing costs rising, it could motivate them to take action."

Still, said Michael Lentz of Keller Williams Realty in Sewell, a one percentage point increase in the rate, say from 4 percent to 5 percent, "increases the principal and interest on a 30-year loan by about 12 percent."

"Buyers at all price levels will feel this, though it is the buyers who are pushing the limits of their debt-to-income ratios that will be most impacted," Lentz said.

Because overall growth in personal income continues to be limited, South Jersey home builder Bruce Paparone called low mortgage rates "an absolute gift."

"The impact of the lower rates has been keeping the cost of housing more affordable," said Paparone, and has allowed certain income levels to purchase bigger homes than they would have been able to afford otherwise.

Typically, low interest rates - and the affordability they make possible - benefit first-time home buyers more than any other group.

And, experts say, the key to the health of the real estate market is a large number of first-timers, who allow current homeowners to buy up or trade down, depending on where they are in life.

"In many cases, interest rates may be the difference between renting and buying," said Frank Dolski of Coldwell Banker Hearthside, in Lahaska, and low ones "were the difference in first-time buyer purchases in 2014, especially the 10 or so families I worked with."

Robert Acuff of Re/Max Services, in Blue Bell, said the slow easing of credit kept "the percentage of first-time home buyers in the market very low in 2014, holding back the overall housing market."

December's announcement by the government-sponsored mortgage-finance giants Fannie Mae and Freddie Mac of 3 percent-down-payment programs for qualified first-time buyers, coupled with continued low interest rates, means that "we should see strengthening" of the market in 2015," Acuff said.

Rates in the 3.75 percent to 4.25-percent range is where Jerome Scarpello, president of Leo Mortgage in Ambler, sees things going over the next six months.

"You may see movements of an eighth to a quarter of a percentage point on any given day, but I don't see any pressing reason why they will spike," Scarpello said.

Said Philadelphia Realtor and mortgage broker Fred Glick: "Very simply, there is no reason for interest rates to go up. [With] turmoil around the world, investors secure their money in U.S. safe havens like mortgages."

In addition, Glick said, "the reason the Federal Reserve raises rates is to slow down an economy, and we are still in a growth mode."

Scott Troxel of Weichert Realtors, in Collegeville, noted that "an increase from 7 percent to 7.5 percent took many buyers out of the market, but with rates hovering around 4 percent, it doesn't seem as much a factor."

Other considerations weighing on the housing market - strict mortgage underwriting requirements, for one - also "seem to be easing, paving the way for an upswing in activity for 2015," Troxel said.

Mortgage rates have an impact on affordability for home buyers, "especially for budget-constrained Americans," Bankrate's McBride said, but the sluggishness of housing in 2014 was largely due to stagnant household incomes, regardless of how low mortgage rates were.

"If 2015 is the year when growth in household income finally materializes," McBride said, "housing will show some signs of life regardless of whether mortgage rates are at 3.75 percent or 4.75 percent."

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