Eggs

Depends on how many eggs you have hatched :) 10 eggs are very rare compare to 5ks and 2ks

I'm finding 10km eggs are more rare now - say the last month or so? Maybe just my luck. But back in October I had a good string of getting 10km.

It's random. I recently talked to a guy who was level 30 and thought 10 km eggs are some in-joke, they don't really exist

Somewhere I read that chances of getting a 10km is around 5%, so 2 out of 100 would be bad luck but still possible.

I do believe the pokestop matters because I was very lucky with a few stops, although I can't tell for sure because now I just hit those stops over and over again without even trying others.

I think I got almost 20 10km eggs out of 340 Total which would be slightly above average

I've hatched 566, and wish there was a way to break down how much of each, but an estimate is that I get a 10K for every 20 or so eggs. Of those 10k's I've hatched, I've still to get a Lapras. Three Snorlax, more Onix, Magmar, etc than I care to recall, one Dratini, no Lapras. I'm level 30.

I have been holding steady at a 4% rate for 10km eggs. Then suddenly this week I got three. That will push me up to 5% (11 of 220).

Still no Lapras, Snorlax, Chansey, or Aerodactyl...

I got 12-15 10km eggs is total. That is out of 142 eggs. Thinking about it that sounds like a lot. However, there was a long period where I was desperately waiting for 10ks. After hatching 2 or 3 before lvl 16 I didn't get any for the next 4 or 5 levels.
It's random. And with randomness comes fluctuation. People often have the wrong idea about randomness and expect some kind of regularity or periodicity.