这是朋友的来信，不过我有7，8年没用过SAS，语法都忘光了，只能求助于各位朋友了。下面是朋友的来信：

－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－

Can I seek your help on SAS PROC MEAN?

Share	Turnover	Date
1	54	2000Q1
1	34	2000Q1
1	64	2000Q1
1	12	2000Q1
1	34	2000Q2
1	22	2000Q2
1	11	2000Q2
1	55	2000Q2
2	31	2000Q1
2	42	2000Q1
2	52	2000Q1
2	53	2000Q1
2	86	2000Q2
2	42	2000Q2
2	32	2000Q2
2	12	2000Q2

What I need is I want to first find the average for each stock for each period.

Then I want to average the stock's turnover average for each period.

As an example, I first need to know stock's 1 turnover average for 2000 Q1.

= (54+34+64+12)/4

= 41

Then I need to know stock's 2 turnover average for 2000 Q1.

= (31+42+52+53)/4

= 44.5

Then I need to find the simple average of all the stock's turnover for 2000 Q1.

= (41+44.5) / 2

= 42.75

Ultimately, I want to find out the 42.75 for each time period.

Right now the way I'm doing it is the following.

proc means no print data = turnover maxdec = 9;

output out = turnover1;

class date share;

variable turnover;

run;

Then I will get something like this

2000Q1 1 41

2 44.5

Then to find the simple average of all the stock's average turnover for 2000Q1, I will manually find the average by adding 41 to 44.5 and then divide it by 2.

However, this is incredibly time consuming because I have around 1000 stocks for each time period. If I sum it up manually and then divide it by the number of stocks.

So, may I ask if you have any simpler methods to help me obtain my final answer?

Thank you so much