The stock market closed at a new 18-month high to close out the week Friday, driven by fresh signs that the economy continues to recover.

While it suggests investors don't expect the economy will slide back into recession, many analysts are still skeptical that the market's gains are sustainable since they have come on relatively low volume. That indicates many investors are still on the sidelines.

Stocks got a boost Friday after reassuring statements from Greece's finance minister and the head of the European Central Bank. Major European indexes closed higher, while the dollar fell against the euro.

Major indexes pulled back briefly after Fitch Ratings cut its view on Greece's debt, but quickly recovered. Stocks have been fluctuating in recent days and the euro has weakened because of concerns that Greece might default.

Rising commodity prices also helped energy and material stocks, pushing indexes higher. Commodities mostly climbed on hopes demand will jump as the economy continues to improve.