Response Rates - This will be a voluntary survey. There may be follow-up telephone contact if response rate is low or if the respondents do not come from a representative portion of the population. The 5 major types of impediments have been identified. Port facility standards as base measures could also be identified to limit errors stemming from reliance on individual judgement. FY 1999 data will be augmented with current electronic data obtained from reliable sources.
Some data is available electronically from other sources.
Noncoverage Error - Port productivity generally does not have major fluctuations from year to year. At least the top 40 ports may not be disputed using the appropriate source, such as the U.S. Army Corps of Engineers port data. The ports at the lowest end of a major port listing could allow for some discrepancy due to possible errors in the source used to identify ports. In order to limit discrepancies in port selection, top ports could be selected based on historical trends. For example, select the top 50 ports based on a five-year historical average.