For productivity analysis, consider this simple C# LINQ query...

var BestCandidates = DataBase.Applicants
        .Where(apl => apl.LookingForJob == "Y")
        .OrderBy(apl => apl.SkillLevel).Take(10)
        .Select(apl => new { apl.FullName, apl.RequestedSalary });

How much lines of COBOL could take to write the equivalent? I think it is more than 100 (I know both languages).

You can do a fair comparison with some reporting and processing exercises. Just make sure that the programmers know their languages well. For instance, a good COBOL programmer can defeat a bad C# programmer in some circumstances, especially in performant batch tasks (i.e. COBOL operates on flat files with direct memory access, therefore cannot equally compare to -let say- RDBMs with memory Objects, unless the programmer knows well about indexes, garbage-collector, direct file access, etc.).

For productivity analysis, consider this simple C# LINQ query:

var BestCandidates = DataBase.Applicants
        .Where(apl => apl.LookingForJob == "Y")
        .OrderBy(apl => apl.SkillLevel)
        .Take(10)
        .Select(apl => new { apl.FullName, apl.RequestedSalary });

How many lines of COBOL would it take to write the equivalent? I think it is more than 100 (I know both languages).

You can do a fair comparison with some reporting and processing exercises. Just make sure that the programmers know their languages well. For instance, a good COBOL programmer can defeat a bad C# programmer in some circumstances, especially in performant batch tasks (i.e. COBOL operates on flat files with direct memory access, therefore cannot equally compare to -let say- RDBMs with memory Objects, unless the programmer knows well about indexes, garbage-collector, direct file access, etc.).