Hi Paige,   Sorry for the confusion. Still new in posting questions here. Your answer is kind of what I need, but I also need to use the forecasted moving average data for the future month forecast, let me show your an example: for proportion data, I only have actuals till 1/8/2019, then I want to have the three month moving average for Sep'19 to Dec'19, using forecasted data as an input too.   date proportion moving_average 1/4/2019 0.1 1/5/2019 0.2 1/6/2019 0.3 1/7/2019 0.25 0.2 (average of 0.1, 0.2, 0.3) 1/8/2019 0.5 0.75 （average of 0.2, 0.3, 0.25) 1/9/2019 0.35 (average of 0.3, 0.25, 0.5) 1/10/2019 0.37 (average of 0.25, 0.5, 0.35(forecasted)) 1/11/2019 0.41 (average of 0.5, 0.35(forecasted), 0.37(forecasted)) 1/12/2019 0.38 (average of 0.35, 0.37, 0.41)  I tried proc expand, which gives exactly the result you offered. I also tried proc arima to compute the moving average. The interesting part by using proc arima is that, for the computed moving average, there will be a slightly difference comparing the result that I manually computed in excel (in 10e-4 level). Since this ratio is needed to multiply a big number (10 billion level), a slight difference will produce a big number after that.    I am wondering if any other simple way we can do the moving average with the forecasted data? ... View more

The data after the third row is what I want to compute using the moving average. Have not figured out how to do it in SAS. Tried both proc expand a proc arima, does not work. ... View more

I want to compute the Jan Feb Mar proportion as for row 4 01/04/2019. So as to the 5 and 6 th rows til 01/12/2022. The proportion is the value of three month moving average. I tried to use proc expand, but it only produces the moving average based on the observed data not the forecasted data. ... View more