Strange Adsense ecpm Jump

So I noticed an interesting ecpm rise in ad revenue last month for one of my sites. Somehow even though I had less impressions and made very fewer posts compared to previous months I ended up earning more due to higher ecpm.

Ex)
April: 200,000 impressions, $1 ecpm = $200 earned (Made 25 posts in April)
May: 100,000 impressions, $3 ecpm = $300 earned (Made 4 posts in May)

What's everyone's analysis on this? I would appreciate a detailed explanation on the matter as I am rather confused on how this happened. Thanks.

 

this can have dozens of reasons without detailed statistics nobody can explain it to you

 

Go ahead and list some of the reasons, but what other stats are needed?

 

compare in the statistics:
clicks
cpc rate
impression rpm
site rpm

i guess you had had more clicks or better rates for the clicks

 

Also look at countries and devices and see if something changed.