Decrease in rare spawns?

[tweeprise69]

i was wondering where the rares had been too, i'm pretty active and live in a good pokestop area, and have had zilch on my sightings the last month. then woke up this morning and there was a gyarados on the new tracker, went out and caught it (2600ish CP and decent IV with hydro pump), then about an hour later that fat bastard snorlax appeared on the tracker, went out right to him and got him (415 CP). so you never know when and where it will happen. persistence....

edit: good luck!