Let's talk numbers, shall we?
To start, let's grab the number 1.92. 1.92 is the number of times more likely someone signing an online petition is to donate to a similar cause after signing. This was quantified by researchers Yu-Hao Lee and Gary Hsieh in their study Does Slacktivism Hurt Activism?: The Effects of Moral Balancing and Consistency in Online Activism.
So, I sign your online petition, I am then almost twice as likely as someone who didn't sign that petition to give money to a cause that is similar to yours.
Notice that didn't read "give money to your organization". Mark that. It'll be on the quiz later.
The researchers also found that I'm more likely to take other actions in support of similar causes after signing your petition, provided those actions don't cost me much.
A great example: signing another online petition.