Whether it’s colored denim at Gap Inc. (GPS.N) or the latest lingerie at Victoria’s Secret, the quest for the latest fashions made apparel retailers the strongest part of the retail universe and helped propel the Thomson Reuters Same Store Sales Index to a 3.9% gain in May, higher than the gain of 3.6% increase that analysts had been forecasting.

While that figure falls below the 5.4% jump in same-store sales registered in May 2011, it’s still a healthy sign for the economy that shoppers were wiling to open their wallets and spend throughout May. Some unseasonably warm weather helped, as consumers headed for the mall to snap up summer clothes and get ready for the hot weather. Mother’s Day promotions shifted into May this year, meaning that spending on gifts for that holiday contributed to the month’s higher same-store sales; lower gasoline prices also helped, freeing up discretionary income that drivers could use at the malls instead. So far, 18 of the 20 retailers in the index have reported their same-store sales for May; the only exceptions are Walgreen (WAG.N) and Rite Aid (RAD.N), which will announce their results next week.

It wasn’t just the big chains that benefitted from consumers’ eagerness to shop last month, however; smaller retailers like Stein Mart (SMRT.O), an apparel retailer, and Stage Stores (SSI.N), a department store, are making a comeback. Both companies beat SSS estimates (Stein Mart saw a gain of 3.1%, significantly better than the projection by analysts that its SSS would climb only 0.5%) and posted record sales. Stage posted its highest increase in same-store sales for May in the last decade, while Stein Mart said it hasn’t seen this kind of increase in sales without a big promotion or an unusual calendar change being responsible. For apparel retailers as a whole, May marked the sixth straight month during which they have been able to report comps of 3% or more. Only two retailers, teen apparel retailer Wet Seal and Kohl’s, a department store, registered negative SSS results for May.

A total of 11 retailers in our universe beat analysts’ expectations for gains in SSS during May, while another five announced SSS results that fell short of those forecasts. However, a few retailers were optimistic about what lies in store for them in the coming months. TJX, for one, said it now expects to post earnings at the high end of its estimated range of 47 cents to 54 cents a share for its fiscal second quarter, ending July 2012.

As we had forecast, the apparel group was clearly the retail industry’s star performer in May, posting SSS growth of 5.4% in May, well above the final estimate of 4.3% and dwarfing the 1.2% increase reported in May 2011. That figure is even higher – 6.8% — if one excludes the heavily weighted Gap from the calculation. (That figure compares to a final ex-Gap forecast of 4.7%, and last May’s ex-Gap SSS gain of 3.4%.) Gap’s SSS rose 2%, below the 3.1% analysts had forecast, thanks to a slump at the company’s Old Navy Division. The company’s Banana Republic brand, in contrast, reported an impressive 8% jump in SSS for May. Companies like Zumiez (ZUMZ.O), TJX Cos. (TJX.N) and Ross Stores (ROST.O) were among the strongest of the apparel retailers in May; the latter two both reported SSS gains of 8%. Once again, Limited Brands (LTD.N) benefited from its ownership of the Victoria’s Secret brand; the latter’s 9.0% gain in SSS enabled Limited itself to report same-store sales climbed 6% across the company’s divisions during May.

The news wasn’t as upbeat among Teen Apparel retailers, however; the sector’s same-store sales were flat in May, although that’s still a better performance than the 0.3% decline analysts had expected. Wet Seal (WTSLA.O), one of the heaviest-weighted components in the sector, was responsible for an outsize portion of that underwhelming performance: its same store sells fell 8.8%, more than the 8.3% decline that analysts had called for. Similarly, The Buckle (BKE.N) registered a weaker-than-expected 0.2% gain in SSS. By far the standout performer in the group was Zumiez, which announced its same-store sales surged 13.7% in May, more than double the gain analysts had projected.

The Discount sector was the second strongest performer from among the retailers, achieving a 4.2% gain in SSS, better than the final estimate of 3.9%. Target took the lead in May, reporting same-store sales climbed 4.4%, a better performance than the final analyst estimate of 3.5%. The retailer has been posting better-than-usual comps in 2012, and May marked the second month this year in which it has led the sector’s list of outperformers. For its part, Costco registered a 4.0% increase in SSS, slightly lower than its 4.3% final estimate. Deflation in gasoline prices and the weakening of many currencies against the dollar put a dent in Costco’s SSS, during the month, however. After taking these negatives into account, and removing them from the equation, Costco’s May SSS gain becomes a more impressive 6%, better than the 4.2% forecast. Fred’s did better than anticipated, posting a 1.3% gain in SSS. As we previously discussed, Thomson Reuters’ proprietary StarMine SmartEstimate score suggests that the company will report earnings of 17 cents a share in the second quarter, nearly a penny higher than analysts are currently projecting. That gives the company a Predicted Surprise of 4.1%.

The Department Store sector registered a 2.0% comp for May, missing its 2.5% final estimate. Most department stores beat analysts’ expectations, with the exception of Kohl’s, one of the heaviest-weighted components in the sector, which saw SSS slump by 4.2%. The group’s standout is Stage Stores, which said it benefited from the shift of Mother’s Day promotions from April last year into May this year. Luxury retailers JW Nordstrom and Saks were among others to announce SSS gains that were ahead of forecast levels, of 5.3% and 4%, respectively. Macy’s also outperformed, announcing a SSS increase of 4.2%, slightly higher than the final estimate of 4%. Macy’s said it saw signs of strength in all its divisions, including Bloomingdales and online sales; the sales of the latter two, combined, rose 42.3% in May compared to their 35.7% advance in May 2011.

Moving into June, retailers should see more favorable weather help them post stronger sales, but they also face some tough comparisons with June 2011, when the SSS index gained a remarkable 7%. Still, this year the June period is a five weeks long, and will include not only the Sunday and Monday of the Memorial Day weekend but also Father’s Day sales. So far in 2012, retailers have posted an average monthly gain of 4.8% in SSS, a robust figure that is toward the high end of the 3% to 5% range in SSS growth recorded throughout 2011. That’s an encouraging sign of consumers’ willingness to loosen their purse strings.

For more on analysts’ changing views of May Sales, please watch this interview with analyst Jharonne Martis. (Link: http://www.reuters.com/news/video?videoId=235754362)