Most national charities can be looked up to see what their "administrative" cost percentage is.
Two of my favorites are the March of Dimes, that actually sends out dimes taped to cards inside their request for money.
WTF?
One similar charity (I think I have mentally blocked the name) had an "in" with the place I used to work (funny, 'cause it was county government), and they were relentless with the asking and asking for "payroll deduction" gifts and sending internal, county emails to the tune of "we haven't heard back from you yet..."
I mean come on....
One year I had had enough, and responded to their outside coordinator, who was sending those emails- "I volunteer for a local 501c3 non-profit that provides labor and funding to vaccinate and sterilize (TNR) feral cats. Are you aware of the size and scope of this national epidemic? (links to info and statistics) If you would be interested in donating to my 501c3, I will donate a matching amount to your 501c3".
I never got another email from that person, not even a reply. Funny how that worked out when the shoe was on the other foot.
Also, once most of them get your contact info, you get bombarded. Good luck trying to make a one-time donation. They are also likely to sell that info to other charities, as why not, it's easy money.
My wife was donating to Toys for Tots, fairly regularly, until she missed a year and got inundated with "why did you stop" letters.
You gotta know my wife....but she ended up personally corresponding with the retired Marine general who ran the entire show, giving him some strongly worded advice, and sending a final check which thereby terminated their relationship.