On its website, the Statesman Journal newspaper $($Salem$,$ Oregon, $2005)$ reports mortgage loan interest rates for $30-$year and $15-$year fixed$-$rate mortgage loans for a number of Willamette Valley lending institutions. Of interest is whether there is any systematic difference between $30-$year rates and $15-$year rates $($expressed as annual percentage rate or APR$)$ and, if there is$,$ what is the size of that difference. The following table displays the $30-$year rate and the $15-$year rate for each of nine lending institutions. Also given is the difference between the $30-$year rate and the $15-$year rate for each lending institution. Use the table to compare the $30-$year rates and the $15-$year rates. Also, calculate the average of the differences between the rates. $($Input the amount as positive value. Round your answer to $4$ decimal places.$)$

Lending Institution $30-$Year $15-$Year Difference

Blue Ribbon Home Mortgage $4\mathrm{.}2246\mathrm{.}472-2\mathrm{.}248$

Coast To Coast Mortgage Lending $5\mathrm{.}2273\mathrm{.}9421\mathrm{.}285$

Community Mortgage Services Inc. $4\mathrm{.}7203\mathrm{.}9280\mathrm{.}792$

Liberty Mortgage $4\mathrm{.}5403\mathrm{.}7710\mathrm{.}769$

Jim Morrison's MBI $4\mathrm{.}0803\mathrm{.}8630\mathrm{.}217$

Professional Valley Mortgage $5\mathrm{.}9295\mathrm{.}992-0\mathrm{.}063$

Mortgage First $3\mathrm{.}0885\mathrm{.}011-1\mathrm{.}923$

Professional Mortgage Corporation $5\mathrm{.}9854\mathrm{.}0481\mathrm{.}937$

Resident Lending Group Inc. $5\mathrm{.}2843\mathrm{.}9221\mathrm{.}362$