Iranians shop at Tehran's ancient Grand Bazaar on July 11, 2016. (Atta Kenare/AFP)

A year ago, the United States and other world powers reached a historic deal with Iran. Economic sanctions that had hobbled the Islamic republic's economy and led to international isolation would be lifted. In return, Iran agreed to terms that would restrict its nuclear capability, including strict international monitoring.

For many in Iran, the immediate response to the agreement was jubilation. As a real deal began to take shape over months of painstaking negotiations, some had taken to the streets to celebrate, honking car horns and waving Iranian flags.

Now, a year after the deal was reached, things don't look quite so rosy in Iran — and a new poll points to growing disillusionment at the pace of change the accord was supposed to bring.

The poll, conducted for the Center for International and Security Studies at Maryland (CISSM) by the independent polling organization IranPoll.com in June, shows that right after the deal was reached on July 14 last year, 76 percent of Iranians approved of it. More remarkable, almost half — 43 percent — approved of it strongly.That figure has since dropped to 63 percent, the poll found, with just 22 percent strongly approving of it.

Economic concerns seem to be paramount in the growing disappointment with the deal. “Iranians appear to have underestimated how much the remaining U.S. sanctions coupled with uncertainty about future U.S. policies would affect their ability to access frozen funds and engage economically with countries besides the United States,” says Nancy Gallagher, interim director of CISSM.

Karim Sadjadpour, a senior analyst at the Carnegie Endowment for International Peace, says that once the excitement of the deal died down, the details were always going to lead to some disappointment. "Given the high expectations people had of the nuclear deal, it was inevitable that it would be followed by a degree of popular disillusionment," Sadjadpour says.

It is clear that for many, expectations were high. Immediately after the deal was signed, 63 percent of Iranians said they expected tangible economic improvements within a year. A year later, 74 percent of Iranians say there has been no improvement.

Many Iranians appear to place the blame at Washington's door: 3 out of 4 Iranians think the United States is actively preventing other countries from normalizing economic relations with Iran. About 72.6 percent of those polled continued to have a very unfavorable view of the U.S. government, and 71.8 say they have little or no confidence that the United States will live up to its obligations.

Whether that view is fair is another question. Low oil prices, not to mention the actions of hard-liners, present other problems for Iran's economy.

"Taking Iran's existing structural economic problems such as high corruption, mismanagement and nepotism into consideration, pouring money into the Iranian economy would be somewhat like pouring water into a sieve," says Meir Javedanfar, an Iran lecturer at the Interdisciplinary Center Herzliya, a university in Israel.

A poll released in February by CISSM also suggested that part of the disappointment was because of a misunderstanding of what the deal had offered. The new survey results seem to show that the trend is continuing. In May 2015, 62.2 percent of Iranians were found to falsely believe that the deal would lead to all U.S. sanctions being lifted. In June 2016, only 23.4 percent believed that.

However, other results suggest that many Iranians still hold mistaken beliefs about the deal. A total of 64.1 percent still believe that the International Atomic Energy Agency cannot access Iranian military sites under the agreement. It can. In fact, the number of Iranians who mistakenly believe this has grown — it was 60.6 percent last year.

It can be difficult to conduct opinion polls in countries with authoritarian regimes. It's possible that many respondents feel unable to speak openly about controversial subjects. However, the CISSM poll is admirable in its scope: 1,007 Iranians were contacted via landline telephone between June 17 and June 27, using a probability-based random digit dialing method that could reach more than 90 percent of households, according IranPoll.com.

There are certainly signs of hope in the report. Forty-six percent of those polled think that there will be a significant improvement in Iran's economy within two years (though just 5 percent say it has already happened), and 49.8 expect a tangible improvement in people's economic situations in that time frame. About 9.9 percent think that Iran's relationship with the United States will significantly improve in the next three years; 21.5 expect a slight improvement.

However, the more immediate consequences of a growing disenchantment may be hard to predict. "The question is whether Iranians will blame the Rouhani government for not delivering, the hard-liners for being obstructionist, or the West for not sufficiently lifting sanctions," Sadjadpour says, pointing out that those inside Iran have a nuanced view of their country's economic problems.

The next presidential election in Iran is scheduled to be held in May 2017. Incumbent Hassan Rouhani, considered a relatively moderate and pragmatic figure who supported the nuclear agreement, has seen declining support over the past year, according to the CISSM poll. The number of those polled who said they had a "very favorable" view of him dropped from 61.2 percent in August 2015 to 37.8 percent in June 2016.

On the other hand, Rouhani's unfavorable ratings remain relatively low, and likely voters told CISSM's pollsters that they would favor him over Mahmoud Ahmadinejad and Mohammad Bagher Ghalibaf, two potential candidates with more conservative views — even though Rouhani has not committed to running.

"Despite the current difficulties, the situation is far better than it was under sanctions," Javedanfar says. "And unless a more moderate candidate is allowed to run in next year's presidential elections, Rouhani still has a good chance of winning."

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