Caterpillar reported a 52-percent year-over-year sales increase in May in documents filed with the Securities and Exchange Commission, although results were slightly weaker than in recent months. May sales were strongest in Europe, Africa and the Middle East where they grew 65 percent.

Although Asia was weaker, it still grew sales 38 percent in the continent.

The Peoria, Ill.-based manufacturer posted annual year-over-year sales growth of 66 percent in April, 61 percent in March and 59 percent in February.