Mortgage interest rates have been pretty attractive for a long stretch of time. So long, in fact, that many homebuyers and homeowners might not realize that rates haven't always been this low. Mortgage interest rates in the 4-percent range were unheard of until 2010, and rates in the 5-percent range were unknown prior to 2003, according to Bankrate.com surveys through the years and a chart of monthly average mortgage interest rates tracked by the Federal Reserve since 1971.Prior to 2003, higher mortgage interest rates were the norm. In the early 1970s, rates hovered in the 7-percent range and spiked up above 9 percent in late 1975, late 1976 and most of 1978. At the end of the decade and throughout the 1980s, mortgage interest rates rarely dipped lower than 10 percent.In the early 1980s, mortgage interest rates brushed the stratospheric highs of 18 percent and even 19 percent. Imagine trying to get a home loan with an interest rate of 18 percent. At that rate, the mortgage interest deduction would be a very lucrative income tax perk, but the monthly payment on a loan would be far more painful than a typical mortgage payment today.During the 1990s, mortgage interest rates ranged from around 7 percent to roughly 9 percent for many years. It was only in 2000 that rates began to fall to earth. They held at less than 9 percent in 2000, less than 8 percent in 2001 and less than 7 percent in 2003.Mortgage interest rates are an important factor in many major financial decisions. When rates are low, it can be a good time to buy a home or refinance an existing mortgage. When rates are high, it can be smart to pay off your mortgage. Rates should also be considered when deciding whether to refinance from a fixed rate to an adjustable-rate mortgage, take out a second loan or tap a home equity line of credit.