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 $3\mathrm{.}9924\mathrm{.}319-0\mathrm{.}327$

Coast To Coast Mortgage Lending $5\mathrm{.}4256\mathrm{.}309-0\mathrm{.}884$

Community Mortgage Services Inc. $3\mathrm{.}7874\mathrm{.}219-0\mathrm{.}432$

Liberty Mortgage $4\mathrm{.}7713\mathrm{.}8110\mathrm{.}960$

Jim Morrison's MBI $3\mathrm{.}9295\mathrm{.}452-1\mathrm{.}523$

Professional Valley Mortgage $3\mathrm{.}0925\mathrm{.}193-2\mathrm{.}101$

Mortgage First $3\mathrm{.}2396\mathrm{.}174-2\mathrm{.}935$

Professional Mortgage Corporation $4\mathrm{.}6564\mathrm{.}6100\mathrm{.}046$

Resident Lending Group Inc. $5\mathrm{.}2155\mathrm{.}251-0\mathrm{.}036$