After every quarter, the nation's biggest banks hold conference calls to review their performance during the previous three months. The calls are typically consumed by various executive officers reading from prepared scripts. But they then leave time for analysts to ask questions and thereby elicit a potentially more candid response.

What follows, in turn, are the five most notable points (both good and bad) made by Citigroup's (NYSE:C) executives during their latest quarterly conference call.

1. The Volker rule and liquidity
The purpose of the Volker rule, which was included in the 2010 Dodd-Frank Act, is to limit banks from making proprietary bets with federally insured deposits. As a result, many of the banks on Wall Street have been forced to reduce their trading activities.

When asked about how this has affected liquidity in the fixed-income market, CEO Michael Corbat responded by saying that in "times of disruption" institutional investors will find it "quite difficult to find liquidity in certain types of assets or in certain asset classes." The insinuation being that banks like Citigroup would otherwise step in to fill the void.

This would be a powerful argument if it weren't for the irrefutable evidence proving it isn't true. The fact of the matter is that in "times of disruption," banks like Citigroup forget their promises to "make markets." They did so in August 2007 when the market for non-agency mortgage-backed securities first froze. They did so in February 2008 by allowing the market for auction-rate securities to seize. And they did so again in September 2008, when even the nation's most respected corporations couldn't issue commercial paper for want of buyers.

2. The Swiss National Bank's decision to unpeg its currency from the euro
Of everything that's happened since the beginning of the year, this has caused the most chaos within the financial industry. Hedge funds and foreign-exchange brokers have been pushed to the brink of insolvency, and it's estimated that Citigroup itself lost upwards of $150 million when the Swiss franc rose vis-a-vis the euro.

The party line on Wall Street is that the move was unexpected; it was a "20-standard-deviation event" said Goldman Sachs' CFO Harvey Schwartz. And Citigroup is toeing the line. According to CEO Corbat, "We'll see what this move does, but I think, clearly, based on market reaction, it came as quite a big surprise."

By Corbat's own admission, however, Citigroup is "a big player in foreign exchange." Thus, to say that its highly compensated traders shouldn't have been prepared for such an eventuality is absurd. Virtually the same thing happened in 1992 when George Soros broke the British pound.

3. An efficiency ratio in the mid-50% range
The efficiency ratio represents the percent of net revenue consumed by a bank's operating expenses. It also happens to be perhaps the single most important metric that investors can use to gauge the soundness of a bank, as, for reasons discussed elsewhere, it weighs heavily on asset quality.

While the objective is generally to be in the 50%-60% range, Citigroup hasn't even come close over the last few years because of elevated legal and regulatory expenses stemming from the financial crisis, an increasing number of trading scandals, and the added operational costs of dealing with toxic assets.

Yet, Citigroup is determined to remedy this. According to CFO John Gerspach, the bank is "committed to delivering [an] efficiency ratio in the mid-50%s." Suffice it to say that you shouldn't believe it until you see it (and even then, it'd be wise to be suspect).

4. The effect of lower oil prices
Of all the major banks, Citigroup is the most internationally oriented. Given the added layer of unquantifiable country and currency risk, it's a miserable business model. That being said, it's the only business model Citigroup's got.

With that in mind, Citigroup's exposure to the recent collapse in oil prices varies with its international exposure. CEO Mike Corbat intimated this by separating its international revenues into three different buckets depending on the direction and magnitude of the impact from lower oil prices:

The countries that I mentioned in terms of being positive probably account for an excess of 65% of our revenues, and you could measure that in 2013 or 2014. If you look at the countries that are most negatively affected, those countries probably constitute somewhere 2%, or less than 2% of our revenues.

The rest fall somewhere in the middle where, "you've got different combinations of where economies overall benefit, yet you have governments that are quite dependent on oil export for revenue generation against their budgets."

5. The cost of new regulations
On a related noted, at the end of the third quarter, Citigroup estimated that its operating expenses would be roughly flat. They then proceeded to rise by $200 million during the fourth quarter.

What was behind the increase? A number of things, one of which was an $180 million expense related to the CCAR process, which banks must now go through each year as a part of their capital planning process.

To be fair, the expense was split between the third and fourth quarters. Moreover, one-third of it is purported to be non-recurring. But either way, it goes to show how much more expensive the new regulatory environment is for the nation's biggest banks.