Ever heard the one about infrastructure week?

As politicians make calls to rectify the decline of U.S. infrastructure investment, a new study from Leah Brooks of George Washington University and Zachary of Liscow of Yale University provides "suggestive evidence" as to how and why infrastructure costs could have changed over time.

After digitizing annual state-level data on interstate highway construction — one of the largest projects in American history — they found that per-mile construction costs increased dramatically over time, tripling between the early 1960s and the 1980s. But why?

Brooks and Liscow ruled out some old theories such as the idea that highway planners procrastinated and left the most geographically challenging routes for last, or that costs for labor and materials changed. Instead, one possible explanation they found is that as incomes and home values rose, so did demand for more expensive interstates. For example, the doubling in real median per capita income between the '60s and '80s accounts for about half the increase in construction costs per mile. States were also building more bridges and ramps as incomes increased. The study suggests all this could have occurred simply because the more money people had, the more willing they were to spend it.

One other factor that the study finds consistent with the data is the rise of the "citizen voice" in the late '60s and early '70s. That includes the growth of environmental activism, the civil rights movement, and homeowners organizing as lobbyists. Basically, more power to the people possibly meant more expensive highway construction. The timing checks out, at least.

The findings, the paper says, are suggestive, but not causal. Still, it looks like a good start in bettering our understanding of infrastructure investment over time. Read the full study here. Tim O'Donnell

After federal investigators arrested Lev Parnas and Igor Fruman last week as they boarded one-way flights to Vienna, their close associate Rudy Giuliani wasn't sure he'd been paid "hundreds of thousands of dollars" by Parnas' fraud-mitigation firm, Fraud Guarantee, as Parnas reportedly attested. On Monday, Giuliani was sure, telling Reuters that Fraud Guarantee paid him half a million dollars for legal and technical consulting work last year.

In their indictment of Parnas and Fruman, federal prosecutors say an unidentified Russian businessman arranged for two payments of $500,000 to be wired from foreign bank accounts to a U.S. account controlled by Fruman in September and October 2018. At least part of that money was allegedly used to try to influence U.S. politicians and candidates on Ukraine policy, in violation of federal law. Giuliani told Reuters he's sure his $500,000 came from "a domestic source," though he did not identify the source or explain how he was "100 percent" certain. "I know beyond any doubt the source of the money is not any questionable source," Giuliani insisted.

The federal prosecutors in Manhattan who indicted Parnas and Fruman are also looking into Giuliani's interactions with the duo and Giuliani's other business in Ukraine. Parnas and Fruman were involved in Giuliani's attempts to pressure Ukraine's government to investigate President Trump's domestic political rival Joe Biden. Giuliani is Trump's personal lawyer and fixer, and his legal troubles could also have serious implications for Trump, CNN's Chris Cuomo explained Monday night.

Giuliani's $500,000 paycheck, for work he said started in August 2018 and was completed by 2019, may not seem exorbitant for such a high-flyer, but one of his main attacks against the Bidens is that fellow lawyer Hunter Biden was apparently paid $50,000 a month by a Ukrainian gas company, ostensibly for similar regulatory compliance work. Peter Weber

In his closing statement Monday night, MSNBC host Chris Hayes offered a few thoughts on "the path of least resistance," where organizations turn a blind eye to bad behavior — the NBA's efforts to appease China, for example, or Republican lawmakers pleading ignorance of President Trump's "bile, bigotry, and rank corruption, and abuse of power." But then Hayes veered out on a limb: "Heck, I feel the tug of it myself as my own news organization is embroiled in a very public controversy over its conduct."

Hayes ran through NBC News' pushback against a new book by Ronan Farrow, Catch and Kill, in which Farrow alleges, among other things, that NBC News tried to kill his bombshell report on Harvey Weinstein not only because of pressure from Weinstein's lawyers but also because of concerns about similar allegations about Matt Lauer, then a big star at NBC News.

Hayes noted that NBC News denies these allegations. He seemed skeptical: "One thing, though, is indisputable. Ronan Farrow walked out of NBC News after working on the Weinstein story and within two months published an incredible article in The New Yorker that not only won a Pulitzer but helped trigger a massive social and cultural reckoning that continues to this day."

"The path of least resistance is always there, beckoning seductively with an entirely plausible cover story — 'You've got bigger fish to fry,' 'This isn't the hill to die on,' 'The story isn't ready,'" Hayes said. "But of course it's the very ease of that path that makes it the enemy of the kind of work we as journalists are supposed to do." Peter Weber

Before he fought to keep his tax returns private, President Trump wanted to release them — to show the world how smart he was for lowering his taxable income, a former adviser told CNN.

Sam Nunberg, who served as Trump's political adviser from 2011 to August 2015, said that over lunch in 2013, Trump said he would be fine with his tax returns being released as part of a presidential bid. Nunberg, who did not see the returns himself, told CNN that Trump "thought he could defend the return. I inferred from the conversation that he believed that it was a lower number and he'd look savvy." Another one of Trump's former senior advisers who joined the pair for lunch corroborated Nunberg's account.

In May 2014, Trump declared on Irish television that he would "absolutely" release his tax returns if he decided to run for office, but Nunberg said that six months later, he talked him out of it. During a meeting, he told Trump that under federal election rules, all he had to do was release a broad financial statement, and could leave the tax returns under wraps. Nunberg told CNN he thought this would protect Trump from opponents who might find something explosive in the tax returns. Trump was fine with this, Nunberg added, because "he wanted to look rich rather than smart."

Trump wouldn't announce he was entering the race for another eight months, and he went on to become the first nominee of a major party not to release their taxes in more than three decades. The president's tax returns are now the focus of several legal challenges, and Trump lost an appeal last week to keep House Democrats from subpoenaing his returns from his longtime accountant. Catherine Garcia

Badlands National Park in South Dakota has expanded its bison range, a move that will "contribute to the health and genetic integrity of the herd and continued health of the prairie," the park said.

The bison now have an additional 22,000 acres of grazing land, for a total of 80,193 acres. The park itself is 244,000 acres, with about 1,200 bison calling it home. On Friday, four bison were moved to the new range, returning to the area for the first time in 150 years.

New fencing and cattle guards were installed in the range, thanks to $743,000 in public and private donations. Due to the expansion, visitors will have "more opportunities for viewing, photographing, and learning about bison in their native habitat on the badlands' iconic and stunning landscape," the park said. Former President Barack Obama named the bison the national mammal in 2016. Catherine Garcia

Moving up from the south, Syrian government troops seized several towns in the northeastern part of the country on Monday, one day after reaching an agreement with the Kurdish-led militia that has held control of the area for several years.

The Kurds and Syria reached the deal after President Trump pulled back U.S. troops from the border, giving Turkey the opportunity to invade Syria and launch an assault on the Kurds. The Kurds and United States worked together to fight the Islamic State in Syria, and the Kurds took control over territory lost by ISIS. After the U.S. retreat, the Kurds turned to the Syrian government for added protection against Turkey. Turkish President Recep Tayyip Erdogan considers the Kurds terrorists.

Syrian government forces were able to take control of multiple towns from the Kurds, including Taqba, which has a hydroelectric dam on the Euphrates. Kurdish fighters spent Monday battling Turkish troops and allied Syrian militias in the border towns of Ras al Ain and Tal Abyad. The recent developments are viewed as victories for Syrian President Bashar al-Assad, who counts Russia and Iran as his allies.

Complicating matters is the fact that the U.S. has about 50 tactical nuclear weapons stored at the Incirlik Air Base in Turkey, 250 miles from the Syrian border. Two U.S. officials told The New York Times that over the weekend, State and Energy Department employees were reviewing plans for getting the weapons out of Turkey. They are "essentially Erdogan's hostages," the Times says, and moving them from Turkey would basically end the alliance between the United States and Turkey. Leaving them is just as problematic, as it puts the weapons and U.S. in a vulnerable position. Read more at The New York Times. Catherine Garcia

Former National Security Adviser John Bolton was so alarmed by a White House–linked effort to pressure Ukraine to investigate Democrats, he told aide Fiona Hill to alert the National Security Council's chief lawyer, Hill told House impeachment investigators in her 10-hour deposition on Monday, The New York Times and The Wall Street Journal report. Specifically, Bolton told Hill, the top NSC staffer on Russia and Eurasian affairs, to notify White House lawyers that Rudy Giuliani, White House acting Chief of Staff Mick Mulvaney, and U.S. Ambassador Gordon Sondland were running a rogue operation, the Times reports.

"I am not part of whatever drug deal Sondland and Mulvaney are cooking up," Bolton reportedly told Hill to relate to the lawyers, after a heated July 10 meeting with Sondland, the U.S. ambassador to the European Union and a key player in the Ukraine pressure campaign, and Ukrainian officals. Before that meeting, Hill reportedly testified, Bolton told her that "Giuliani's a hand grenade who's going to blow everybody up." Giuliani, President Trump's personal lawyer, is now under federal criminal investigation for his work in Ukraine, the Journal reported Monday. Sondland is scheduled to be deposed on Thursday.

House investigators are now trying to decide whether to question Bolton, The Washington Post reports.

Hill also testified that he had strongly opposed Giuliani's successful push to have Trump remove America's ambassador to Kyiv, Marie Yovanovitch, who had a reputation for fighting corruption in Ukraine. "I don't know Fiona and can't figure out what she is talking about," Giuliani told the Post on Monday night, adding that he believes she was out of the loop when it came to Ukraine, at least compared with Sondland. "She just didn't know," Giuliani said, reiterating his assertion that he was working on orders from the State Department. Peter Weber

Update, 12:47 a.m.: This article has been updated based on a clarification by the Times: