I have a continuous variable in some panel data (xtset by id and year over 5 years) that I would like to create quintiles of:

Code:
. sum O_SDQpeerprobs_y

    Variable |        Obs        Mean    Std. Dev.       Min        Max
-------------+---------------------------------------------------------
O_SDQpeerp~y |     32,090    1.070988    1.407768          0         10
I use the function xtile() from egenmore (SSC) to do this as below:

Code:
. egen O_SDQpeerprobs_yQ5 = xtile(O_SDQpeerprobs_y), nq(5)
(23580 missing values generated)
However, when I go to examine the data it has quintile 1, 3, 4 and 5. Quintile 2 is missing, can anyone help me to understand why this is happening and how to fix it?

Code:
. tab O_SDQpeerprobs_y O_SDQpeerprobs_yQ5

O_SDQpeerp |             O_SDQpeerprobs_yQ5
    robs_y |         1          3          4          5 |     Total
-----------+--------------------------------------------+----------
         0 |    15,189          0          0          0 |    15,189 
         1 |         0      7,808          0          0 |     7,808 
         2 |         0          0      4,718          0 |     4,718 
         3 |         0          0          0      2,200 |     2,200 
         4 |         0          0          0      1,188 |     1,188 
         5 |         0          0          0        492 |       492 
         6 |         0          0          0        278 |       278 
         7 |         0          0          0        131 |       131 
         8 |         0          0          0         57 |        57 
         9 |         0          0          0         19 |        19 
        10 |         0          0          0         10 |        10 
-----------+--------------------------------------------+----------
     Total |    15,189      7,808      4,718      4,375 |    32,090

Thank you,

John