I average about 14%, but that doesn't include the '82s (which I separate out). I also get somewhere between 5 and 10 wheats per boxes, though I got 20 out of a box a few weeks ago. I once got a bunch of rolls (loose), of which 4 were solid 1979-d cents in uncirculated condition. I have been through roughly 100,000 pennies, all by hand, and my oldest find is a 1910, with several in the teens and twenties (though most are 1950s). I once got a gem-BU 1958 penny - almost went by it because it looked so new, but I happened to flip it over and saw those beautiful stalks of wheat, so it got put into its own holder.
1 in 7 isn't really that bad, there have been 29 years of copper-plated zinc production, and they have been the highest mintage years, so that's a decent percentage. It'll only deteriorate from here, esp. if the gov't stops making pennies altogether - then they'll all disappear in a couple of years.