Creating a variable by relative difference of two columns

[Sonnen Blume]

Hi,
I have data on employment duration of employee 1 and 2 measured in months. I want to create a new variable to see whether emlpoyee 1 has been working for longer/shorter compared to employee 2. I tried

difference =abs(emp1-emp2)

but it doesn't look like what I'm looking for. Is there any way to do this in Stata 14.
Thanks in advance for your help!

* Example generated by -dataex-. To install: ssc install dataex
clear
input byte(emp1 emp2)
35 44
37 45
32 43
38  .
32 43
27 30
21 25
28 38
38 45
35 45
33 44
23 27
42 44
49 50
42 48
34 42
25 31
40 46
34 50
47 56
21 27
33 41
25 29
24 27
30 41
31 32
15 28
30 30
38 43
43 52
32 33
34 48
47 50
32 37
21 20
36 38
35 45
41 53
35 50
33 38
15 17
41 53
20 20
42 61
29 43
44 52
43 47
33 44
48 53
20 23
37 41
20 26
33 41
37 44
27 39
31 45
27 31
19 24
31 43
22 33
24 28
44 65
34 33
18 28
38 46
34 40
31 36
29 32
20 22
37 43
26 29
28 36
33 39
32 45
48 56
24 29
41 47
37 48
28 31
19 26
28 39
43  .
41 46
47 51
18 25
30 35
26 28
27 30
27 28
17 22
40 47
19 26
20 30
42 48
18 25
48 56
40 43
37 52
23 30
34 39
end
label values v730 V730