non-response       
noun [ C or U ] (also non-response) uk/ˌnɒn.rɪˈspɒns/ us/ˌnɑːn.rɪˈspɑːns/
 无回复;不理睬
a failure to give an answer or reaction
  I think your non-response to my question is extremely rude. 我认为你不回答我的问题是非常粗鲁的。 
 The information from the survey is flawed because of the high rates of non-response. 
 - More examples
 - The problem has become more serious because of the non-response from governments around the world.
 - Given the high number of non-responses, it is hard to draw any conclusions from the data.
 - Nonresponse was reduced when the questionnaire was put online.
 - The nonresponse rate for the survey was less than 3%.