Tiny, but unexpected performance difference between variable

In a discussion whether to use a property or a variable, I expected that a variable would be faster than a property as it doesn't have the overhead of setters/getters so I ran a test comparing assigning a variable vs a property.

Turns out that as long as no setters are involved a property is the fastest and a local variable is the slowest. Once the setter is added a property is much slower as expected.

Is this a known difference ?

Before this test I assumed a local variable to be the fastest of them all. Did I make a mistake in my test ?

lqqqqqqqq Information qqqqqqqqqk 
x   106 :Local var x 
x    85 :global var x 
x    55 :property x 
x   522 :property empty set x 
x   559 :property set x 
x qqqqqqqqqqqqqqqqqqqqqqqqqqqq x 

Related  thread  Property or Variable ?

class test:

    &scoped-define testcount 100000
    define variable myVar as char no-undo.

    define private property myProp as char no-undo
        get.
        set.

    define private property mySetPropNocode as char no-undo
        get.
        set (input istring as char):
        end set.

    define private property mySetProp as char no-undo
        get.
        set (input istring as char):
            mySetProp = istring.
        end set.

    constructor test():
        def var i as int no-undo.
        def var localVar as char.
        define variable Results as character no-undo.

        etime(yes).
        do i = 1 to {&testcount}:
            localVar = string(i).
        end.
        results = subst("&1&2 :Local var    ~n", results, string(etime, "zzzzz9")).

        etime(yes).
        do i = 1 to {&testcount}:
            myVar = string(i).
        end.
        results = subst("&1&2 :global var   ~n", results, string(etime, "zzzzz9")).

        etime(yes).
        do i = 1 to {&testcount}:
            myProp = string(i).
        end.
        results = subst("&1&2 :property     ~n", results, string(etime, "zzzzz9")).

        etime(yes).
        do i = 1 to {&testcount}:
            mySetPropNoCode = string(i).
        end.
        results = subst("&1&2 :property empty set ~n", results, string(etime, "zzzzz9")).

        etime(yes).
        do i = 1 to {&testcount}:
            mySetProp = string(i).
        end.
        results = subst("&1&2 :property set ~n", results, string(etime, "zzzzz9")).

        message Results
            view-as alert-box information buttons ok.
    end.

end class.