My first playthrough to level 70 had alot of attacks...between level 50 and 70 I was often getting two settlements attacked at the same time. I was getting so many attacks that I was just tired of responding to them and breaking my immersion with exploring.

However, my second playthrough to level 29 so far and I have had only 5 attacks. One was a double on two different settlements at the same time though.

I have yet to figure out why there is a difference.

Also, I cannot figure out how big a settlement can get. I had to turn off the beacons during my first playthrough when I got over 30 settlers. This time around I have tons of food, water, ammenities, shops and defense and my settlers do not show up.

The higher your Defense Rating is over Food + Water, the lower the chance you'll be attacked. There also seems to be some variance, of course, but that's the base test.

As for max population, it is normally CHA + 10. This can be boosted with various CHA boosting garb and chems. However, there is also a definite bug (one of many) specific to Playstation 4 version where dozens of settlers keep coming even with no attention being paid to the settlement. This goes along with the supply duplication exploit on PS4 and perhaps others.

I hardly ever get them. I neglect half my settlements entirely, and the ones I don't I fortify their defenses quite a bit. I kind of wish they'd happen more often. I'm level 49 and I've only had 3 attacks so far.

Cutter, scrap all defenses, arm every settler with a minigun, sit back and watch the show.

I just hit level 50 today and my settlements have suddenly become a hotspot for raiders and gunners, I got like 4 more settlements attacks in a row one after the other today. Hangman's Alley, Bunker Hill the Lighthouse and Finch farm. I developed Hangman's a little, the light house is my base of operations, and I never go to Finch farm and haven't built hardly anything there, just a fast travel point on the freeway. Same with Bunker Hill, I never go there. No rhyme or reason to the location of the attacks, it seems, but they've definitely increased in frequency once I hit level 50.