XML versus ASN.1

I don't know how widely the ASN.1 Packed Encoding Rules (PER) are used but here's an example of how much more verbose XML can be than PER.

Here's a simple ASN.1 definition:

FooBaz {1 2 0 0 6 3} DEFINITIONS ::=
 BEGIN
    T1 ::= INTEGER (25..30)

    Test1 ::=
       SEQUENCE {
          first  T1,
          second T1
       }
  
    Test2 ::=
       SEQUENCE {
          first2  [0] T1 OPTIONAL,
          second2 [1] T1 OPTIONAL
       }
  
    Integer11 ::= INTEGER (0..32000)    
  
    Test3 ::=
       SEQUENCE {
          first  T1,
          second T1,
          third Integer11,
          fourth Integer11
       }
 END

Here's an encoding using XML:

<Test3>
   <first>29</first>
   <second>30</second>
   <third>63</third>
   <fourth>31000</fourth>
</Test3>

Here's the PER. Note that it fits into 36 bits so the last 12 are irrelevant.

9401 ff91 8000

I make that 36 bits for PER and 112*8 = 896 bits for XML, a ratio of 1:25.