I have a problem with dataset, that is the fact that in some time series data start to appear in a certain year but I need the value of those time series for the precedent year. For example, in the TFP time series for Euro Area datas starts to appear only in 1995, but since I have to calculate the TFP growth, I need data for 1994 for certain countries. So, my question is: how trying to estimate those missing values? I'm thinking to use a four-period backward looking moving average (i.e.: the average of the first four values that I have). Do you think it is correct? Are there other methods to do that? Thank you in advance.