Francisco Pacheco-Camacho was an exemplary prisoner. Serving his sentence of a year and a day, he earned the maximum number of good time credits permissible under federal law. Pacheco says that number is fifty-four days, but Bureau of Prisons (BOP) regulations allow him only forty-seven. This appeal is about the disputed seven days. 1
I
A federal prisoner may receive “up to fifty-four days at the end of each year of the prisoner’s term of imprisonment, beginning at the end of the first year of the term,” subject to the BOP’s determination that “during that year, the prisoner has displayed exemplary compliance with institutional disciplinary regulations.” 18 U.S.C. § 3624(b)(1). Under this scheme, at the end of each year, the BOP determines whether the prisoner has been naughty or nice. If the latter, it may award him credit for an extra fifty-four days towards the remainder of his sentence.
The counting gets a bit tricky during the last year — or portion of a year — of the prisoner’s sentence, because he obviously can’t wait until the year’s end to receive his credit. Recognizing this, the law provides that “credit for the last year or portion of a year of the term of imprisonment shall be prorated and credited within the last six weeks of the sentence.” Id. The BOP has promulgated an implementing regulation, which adopts the amount of time actually served by a prisoner as the basis for the proration. 28 C.F.R. § 523.20. The regulation consequently prorates the fifty-four days of credit a year earned by the model prisoner to 0.148 day *1268 of credit for every actual day served during good behavior (54/365 = 0.148). At this rate, a prisoner who behaves himself may complete a sentence of a year and a day after serving 319 days in prison. At that point, the prisoner will have earned forty-seven days of good time credits (319 x 0.148 = 47.212), which, when added to time served, would make up the full 366 days of his sentence (319 + 47 = 366). 2
Pacheco argues that this formula conflicts with the governing statute. In his view, when the statute awards fifty-four days “at the end of each year of the prisoner’s term of imprisonment,” this award should be based on the sentence imposed, without regard to the time actually served. According to Pacheco, “term of imprisonment” has a particular meaning. Because “[t]he term ‘imprisonment’ consistently is used to refer to a penalty or sentence,”
United States v. Morales-Alejo,
II
We review Pacheco’s claim that the BOP regulations have improperly deprived him of his duly-earned good time credits with the deference that must be accorded to an agency’s interpretation of the statute it administers. Because the BOP regulation in question, 28 C.F.R. § 523.20, was adopted through the notiee- and-comment procedure, it is entitled to the full deference mandated by
Chevron U.S.A. Inc. v. Natural Res. Def. Council, Inc.,
In this case, the words of the statute do not provide clear guidance as to what the phrase “term of imprisonment” means. At the very least, the plain language of section 3624(b) certainly does not compel Pacheco’s conclusion that the “term of imprisonment” 'must refer to a sentence imposed in the judgment, as opposed to the time actually served. If anything, this reading is inconsistent with the statute, which provides that “credit for the last year ... of the term of imprisonment shall be prorated ...” 18 U.S.C. § 3624(b)(1) (emphasis added). Instead of a prorated portion, Pacheco wants the entire fifty-four days of credit — even though he never served the full 365 days. Whereas the *1269 model prisoner will ordinarily receive his fifty-four-day credit after complying with prison disciplinary rules for 365 days, under Pacheco’s reading, a prisoner who serves 311 days would receive the same number of credits for exhibiting good behavior over only eighty-five percent of the year. Pacheco’s interpretation would therefore confer upon the prisoner a bonus during his last year of imprisonment. Nothing in the statute clearly suggests that Congress intended to give the prisoner such a windfall in his last year.
Contrary to Pacheco’s contention,
United States v. Morales-Alejo,
Ill
As the language of section 3624(b) does not make clear whether the sentence imposed or the time served should be used as the basis of proration, we consider whether legislative history removes the ambiguity.
See Am. Rivers v. Fed. Energy Reg. Comm’n,
In support of his interpretation, Pacheco relies on the fact that the statutory predecessor to section 3624 computed good time credits after every month served, and that by enacting the new statute, Congress sought to simplify this computation. See Continuing Appropriations, 1985 — Com prehensive Crime Control Act of 198b, Sen. Rep. No. 98-225 (1984), reprinted in 1984 U.S.C.C.A.N. 3182, 3329-30. In Pacheco’s view, the BOP’s formula is a return to the more complicated scheme of calculating credits on the basis of time actually served, and is therefore contrary to congressional intent.
We find this argument unpersuasive. Under the earlier scheme, the good time credits were calculated at different monthly rates, depending on the length of the prison term, and prison officials had discretion to withhold and restore credits depending on the inmate’s subsequent behavior. That system did not allow a prisoner to estimate with certainty the time of his release. The new system, embodied in 18 U.S.C. § 3624(b), envisioned that prisoners would be able to do so.
While Congress intended the new system to be simpler than that under the previous law, it did not eliminate the pro-ration of good time credits during the last year of the sentence. If Congress’s sole goal had been simplicity, it could have chosen not to award any good time credits during the last year of imprisonment (as it does for sentences of a year or less), or to *1270 award the full fifty-four days regardless of whether or not the prisoner serves the full year in prison. Instead, Congress chose to tolerate the additional complexity in order to arrive at a more equitable result. Far from mandating Pacheco’s interpretation, congressional desire to strike a balance between simplicity and fairness, as evidenced by legislative history, lends additional support to the BOP’s regulation.
IV
Finding the meaning of “term of imprisonment,” as used in section 3624(b), to be ambiguous, we proceed to the second step of the
Chevron
analysis, examining whether the BOP regulation is “based on a permissible construction of the statute.”
Chevron,
As we have held in the context of the doctrine of credit for time at liberty, “[i]t is the administrative responsibility of the Attorney General, the Department of Justice, and the Bureau of Prisons to compute sentences and apply credit where it is due.”
United States v. Martinez,
In determining whether a regulation is reasonable, we “need not conclude that the agency construction was the only one it permissibly could have adopted to uphold the construction, or even the reading [we] would have reached if the question initially had arisen in a judicial proceeding.”
Id.
at 843 n. 11,
As the discussion in Parts II and III of our opinion shows, the BOP’s interpretation clearly meets this standard. This interpretation comports with the statutory language of section 3624(b), and does not subvert the statutory design. It establishes an effective and fair 'prorating scheme, enabling inmates to calculate with reasonable certainty the end of their im *1271 prisonment, while preventing certain prisoners from receiving disproportionate good time credits merely because their sentence happens to equal a year and a day.
We are not persuaded by Pacheco’s contention that the language of the preceding subsection of the statute, section 3624(a), supports his interpretation of section 3624(b). Section 3624(a) states that a prisoner “shall be released by the Bureau of Prisons on the date of the expiration of the prisoner’s term of imprisonment, less any time credited toward the service of the prisoner’s sentence as provided in subsection (b).” 18 U.S.C. § 3624(a). Pacheco asserts that “term of imprisonment,” as used in that subsection, can only be interpreted as referring to the length of a sentence, rather than to the term served. Because statutory terms should be interpreted, whenever possible, with an eye to intra-statutory consistency,
Sullivan v. Stroop,
Given that our holding hinges on the deference due to the BOP, rather than on a fresh interpretation of the statute in question, we need not decide the meaning of “term of imprisonment” in section 3624(a) and its impact upon the subsection before us. We note, however, that Pacheco’s argument is undermined by
United States v. Johnson,
V
While arguing that his interpretation of the statute is clear from the text and supported by legislative history, Pacheco also suggests, in the alternative, that his interpretation is plausible and should be preferred to that of the BOP because of the rule of lenity. The rule of lenity ensures that the penal laws will be sufficiently clear, so that individuals do not accidentally run afoul of them and courts do not impose prohibitions greater than the legislature intendéd.
See United States v. Bass,
AFFIRMED.
Notes
. We have already ruled on Pacheco’s emergency motion for consideration on the merits in our order of February 23, 2001, affirming the judgment of the district court. We now explain our reasons for doing so.
. The calculation method is spelled out in detail in the BOP Program Statement, which explains how the proration works in various situations. BOP Program Statement 5880.28 at 1-45 (1992). Because these internal guidelines merely provide examples of how the proration mechanism of 28 C.F.R. § 523.20 is applied, and do not purport to alter the BOP regulations themselves, our review does not address them.
