Hello Statalist members,

i am analysing a firm panel where I am regressing the number of high skilled employees on three dummies and some control variables. One of them is investment (in Euros). I am using a Poisson fixed effects regression and Stata 13. The coefficient for investment is 9.60e-11, which is basically zero (0.000 when I round coefficient to three decimals, same for the confidence interval and standard error) and I am wondering what this means and how to interpret it? If there is no relationship between the variables it should not be statistically significant or am I mistaken?

Code:
 xtpoisson highskill investict product_inno process_inno lnturnover lnavwages collective lnexportshare investment i.year, fe vce(robust)
note: 224 groups (224 obs) dropped because of only one obs per group
note: 10180 groups (49161 obs) dropped because of all zero outcomes

Iteration 0:   log pseudolikelihood =  -120765.5  
Iteration 1:   log pseudolikelihood = -108313.47  
Iteration 2:   log pseudolikelihood = -108273.22  
Iteration 3:   log pseudolikelihood = -108273.22  

Conditional fixed-effects Poisson regression    Number of obs     =     53,130
Group variable: idnum                           Number of groups  =      9,405

                                                Obs per group:
                                                              min =          2
                                                              avg =        5.6
                                                              max =         12

                                                Wald chi2(18)     =     161.63
Log pseudolikelihood  = -108273.22              Prob > chi2       =     0.0000

                                   (Std. Err. adjusted for clustering on idnum)
-------------------------------------------------------------------------------
              |               Robust
    highskill |      Coef.   Std. Err.      z    P>|z|     [95% Conf. Interval]
--------------+----------------------------------------------------------------
    investict |   .0256531    .010968     2.34   0.019     .0041561      .04715
 product_inno |  -.0059202   .0283482    -0.21   0.835    -.0614816    .0496412
 process_inno |    .035324   .0168719     2.09   0.036     .0022557    .0683923
   lnturnover |   .2225503    .038659     5.76   0.000     .1467802    .2983205
    lnavwages |   .0048915   .0269775     0.18   0.856    -.0479835    .0577664
   collective |  -.0064905   .0217641    -0.30   0.766    -.0491475    .0361664
lnexportshare |   .0113623   .0076189     1.49   0.136    -.0035705    .0262951
   investment |   9.60e-11   2.14e-11     4.50   0.000     5.42e-11    1.38e-10
              |
         year |
        2008  |   .0124656   .0145073     0.86   0.390    -.0159682    .0408995
        2009  |   .0502652   .0342328     1.47   0.142    -.0168299    .1173603
        2010  |   .0917918   .0202746     4.53   0.000     .0520543    .1315292
        2011  |    .156842   .0540877     2.90   0.004     .0508321    .2628518
        2012  |   .2284362   .0607472     3.76   0.000     .1093738    .3474985
        2013  |   .2258726   .0640781     3.52   0.000     .1002819    .3514634
        2014  |    .271107    .067284     4.03   0.000     .1392328    .4029813
        2015  |   .2600914   .0546444     4.76   0.000     .1529904    .3671923
        2016  |   .2684858   .0528786     5.08   0.000     .1648456    .3721261
        2017  |   .3187303   .0638673     4.99   0.000     .1935527     .443908
        2018  |   .3404339   .0668107     5.10   0.000     .2094874    .4713804
-------------------------------------------------------------------------------
If anyone can tell me how to interpret the zero coefficient this would be of great help, I have tried research online as well as econometrics books but I have never found an example case like this with a coefficient being zero.

Thanks,

Helen