TABLE D-4.--Trend in May and July pond indexes by strata, 
North Dakota, South Dakota, and Minnesota, 1959-63 
[Index numbers in thousands | 
Stratum 
Year 


Average, 1962-63 -- 
Percent change, 1963 from 
Average, 1962-63 
Percent change, 1963 from 
1962-~-------------+-- 
Average --------------- 
Note:--Due to a change in recording water areas in 1962, 1962 July 
pond index is not comparable to previous counts. 
106 
