estimates of use can be updated annually for perhaps 3 to 4 years based on self- 

 registration information only, without interviewing entering visitors. It would be 

 necessary only to solve the regression equation or apply the ratio estimate "correction 

 factors" using registration information obtained each year. Thus, the average annual 

 cost would amount to approximately $3,000, including about $300 annually for servicing 

 registration stations, travel, and administration, which managers would probably have 

 to spend anyway. The same registration system should continue in use for the period of 

 time that use estimates are updated in this manner. 



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