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Look for the complete U.S. Stamp Market Index once per month in Linn's Stamp News. Michael Laurence comments on this notable achievement in his Editor's Choice column of this issue. Overall, Linn's U.S. Stamp Market Index crept up a statistically insignificant 0.03 percent for the month, from 643.6 to 643.8. Nineteenth-century stamps rose a negligible 0.4 percent in April and now stand 7.1 percent above the April 2000 level. Price increases reflect a general strengthening of prices for fine to very fine stamps.