UN: Peru reduces extreme poverty by half?

I'm watching a presentation by Peruvian President Alan Garcia and United Nations representatives about a big accomplishment: 

In 1991, 23% of Peruvians lived in extreme poverty. Today, 12.6% of Peruvians live in extreme poverty--only a percentage shy of the country's 2015 goal of 11.5%. 

While the United Nations report signaled that malnutrition is still a big problem in Peru, advances have been made in labor, education and rural development. 

But a July article in El Comercio, one of the national papers here, points out flaws in the methods of measuring the depth of poverty here, putting in doubt the level of today's positive development. 

The National Institute of Information and Statistics, on whose numbers this report is based, has not updated and reevaluated the canasta basica (basic food basket) from the 1991 prices and products. So when they count how many Peruvian can buy this canasta basica, the Institute is measuring on outdated standards, and receiving inaccurate numbers. 

Also, other experts point out that the Institute has not taken into account the difference between rural and urban prices for the same products in the canasta basica.

Considering these flaws, the article argues that the true level of poverty in Peru is still unknown.